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已有 9206 次阅读 2008-4-25 08:38 |个人分类:书海拾贝|系统分类:观点评述

(见《Physics in Perspective》,Vol.1, pp224-225, 1999
 
John Archibald Wheeler with Kenneth Ford
Geons, Black Holes and Quantum Foam, A Life in Physics.
New York and London: W.W. Norton, 1998, 380 pages. $27.95 (cloth).
 
Sometime in the late fifties, Samuel Goudsmit, then Editor-in-Chief of The Physical Re6iew, let it be known that he was about to publish an editorial in Physical Review Letters saying that the journal would no longer accept papers on gravitation theory “or other fundamental theory.” Only the intervention of John Wheeler prevented this editorial from appearing. This incident illustrates two things: how far we have come since those days, and the stature of John Wheeler.
 
Young researchers find it almost unbelievable that Goudsmit’s attitude toward gravity theory could ever have been common. They are told that the strongest argument for string theory (or M theory) is that it alone is capable of uniting gravity and the quantum. Wheeler was perhaps the foremost champion of this unification (“fiery marriage” he called it). Almost single-handedly, starting in the mid-fifties, he determined to wrench gravity theory from the quiet backwaters where it had drifted for three decades and drag it into the mainstream of physics. There were others who had the same ambition, but the momentum that he provided was decisive. Within a dozen years his fabulous gang of students, together with youngsters like Roger Penrose and Stephen Hawking from the other side of the Atlantic, had forged gravity theory into an exciting new discipline with all sorts of fantastic implications. Even his earlier student, Richard Feynman, was moved to start thinking about quantum gravity, an effort that ultimately had its greatest impact on Yang-Mills theory and the Standard Model.
 
Much of the story behind this activity is set forth in this book: The first course Wheeler taught in relativity in 1952. Taking his class to visit Einstein. “Geons” (Dick Feynman called him Geon Wheeler). Mass without mass. Charge without charge. Gravitational waves and Joseph Weber’s antenna. Hugh Everett and the many worlds interpretation of quantum mechanics. Gravitational collapse. Black Holes and Bekenstein’s entropy. Topology and quantum foam. The great book with Misner and Thorne. Along with this story go vignettes of his many friends, starting with his hero, Niels Bohr, in Copenhagen in 1934. Many of these sketches are interspersed with descriptions and explanations of physical phenomena in layman’s terms, as well as with purely autobiographical material: His early childhood in Glendale, California, and then in Youngstown, Ohio, Washington, D.C. and Baltimore. His lifelong love of explosives. Scholarship to Johns Hopkins, where he was both an undergraduate and graduate student. Postdoctoral work with Gregory Breit and Niels Bohr. Marriage to Janette Hegner. First faculty position at the University of North Carolina at Chapel Hill. His move to Princeton and his work with Feynman. Fission and the liquid-drop model. On through the war years to his decades-long consuming interest in general relativity. Retirement from Princeton, the move to Texas, and the years past age 75, still pondering the secrets of the quantum.
 
Wheeler has led a very full life. And yet his book is infused with a sombre tone, no inkling of which is suggested by its title. Of its sixteen chapters only six deal with geons, black holes or quantum foam. Five deal with the Bomb.
 
The book opens on the eve of the World War II and the effort to get President Roosevelt moving on secret fission research. Wheeler had a passion about the bomb. Referring to his brother, who was killed in action in the Italian campaign and is buried in a military cemetery near Florence, he writes “Every time I visit Joe’s grave, I am reminded that he is one of many – one of many millions, I calculate, both soldiers and civilians – whose lives might have been spared if the Allies had developed the atomic bomb a year sooner.”
 
The story moves on: To the prediction, by the fission model of Bohr and Wheeler, of the existence of the fissile element plutonium. The production of plutonium in kilogram quantities at Hanford, Washington, where Wheeler spent much of his time on the Manhattan Project. The Manhattan Project itself. Development of the first nuclear reactor in Chicago. Time in Wilmington, Delaware, with DuPont, the contractors for the Hanford production plant. The postwar years at Los Alamos and the design of the H-bomb. The beginnings of antagonistic reactions from his colleagues. His defensiveness in regard to his views on civil defense, missile defense, nuclear power, weapons testing, and defense work in general. Loyalty oaths. Project Matterhorn. Eniwetok. Sputnik. His support of the “missile gap” hypothesis (which he excuses by saying that, for him, “missile gap” really meant “military technology gap”). Adviser to NATO’s Standing Committee on Scientific and Technical Personnel. His support of NATO Summer Institutes modelled on the famous Les Houches Summer School. Project 137. The Jason group. Support of tactical nuclear weapons and “A Doctrine for Limited War.” Receipt of the Enrico Fermi Award. Finding himself  “out of step with some of my faculty colleagues” at Princeton.
 
It is clear that Wheeler carries scars on his soul which, on occasion, cause him to react in surprising ways. One day I told him of a letter I had received in the Navy in early August 1945. It was from my father, a country doctor turned army medical officer. Reacting to the news of the atomic blasts in Japan, he wrote, “It is a terrible thing to think of the innocent children being painfully burned or wounded and killed by that terrific bomb explosion.” My father added that he hoped it would all end soon. I told Wheeler that my father’s were the first words of compassion I had read or heard from an American. Wheeler reacted as if stung, as if I were attacking him personally.
 
What has nevertheless sustained Wheeler in his relations with his colleagues is his unfailing smile and genuine interest. Every physicist, and many non-physicists, will want to read his book. Being a physicist, and hence always ready for an argument, I cannot resist closing by tweaking Wheeler’s toes on three technical points:
 
1. Quantum foam: This concept has never made sense to me. If spacetime were to be regarded as a membrane embedded in a higher dimensional space, then the concept of changing topology as a dynamical process, or “summing over topologies” in a Feynman functional integral, might make sense. But in no other way.
 
2. Closed vs. open: On page 325 Wheeler mistakenly assumes that the mass density in a closed universe must be greater than a critical amount. This is an old error that cosmologists are beginning to acknowledge, and that I love to point out.
 
3. Many Worlds: Wheeler does not like these words that I coined to describe the interpretation of quantum mechanics put forward by his student Hugh Everett III (see p. 270). But in his “Assessment of Everett’s ‘Relative State’ Formulation of Quantum Theory,” Rev. Mod Phys., 29, (1957), 463, he wrote: “The kind of physics that goes on does not adjust itself to the available terminology; the terminology has to adjust itself in accordance with the kind of physics that goes on.” I have always invited him to adjust, with whatever terminology he chooses, to the real spirit of Everett’s vision.
 
Finally, I am grateful to John for never once mentioning an equation, to which our names are jointly attached, that I regard, for many reasons, as a hopelessly defective equation.
 
Bryce DeWitt
Department of Physics
University of Texas at Austin
Austin, TX 78712-1081 USA
e-mail: dewitt@physics.utexas.edu


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