by Kip S. Thorne
Forward by Stephen Hawking
Reviewed by Michael J. Mehl
After reading the introduction and the science-fiction like prologue of Kip Thorne's Black Holes and Time Warps, I assumed that this was a standard popularization of the topic, on the order of James Gleick's popular books, Chaos: Making of a New Science. You know, a bit of the science, and lots of "sense of wonder."
Someplace in Chapter Two I realized that this book is much more than that. This is not only a "gosh, wow, whee!" book, it also contains a history of physics in the first half of the twentieth century physics, through the end of the Manhattan project, and Thorne's own professional biography.
What we call "modern" physics dates from 1905, when Albert Einstein published a series of papers describing: special relativity, which reconciled Isaac Newton's laws, the triumph of 17th century theoretical physics, with James Clerk Maxwell's equations, the triumph of the 19th century theoretical physics; the photoelectric effect, showing that light sometimes behaves as a particle, providing one of the supports for the development of quantum mechanics; and the molecular basis of Brownian motion, conclusively proving the matter is indeed made up of atoms and molecules.
In November, 1915, in the middle of World War I, Einstein put the finishing touches on his "General" theory of relativity, showing that gravitation can be considered as the "warping" of space by matter. By the following January one of the first "outrageous" point of the theory became apparent. While serving with the on the Russian front with the German Army, Karl Schwarzschild, a distinguished astronomer, constructed his solution for the gravitational field of a spherical star, the "Schwarzschild geometry". The most intriguing feature of this geometry was its "singularity," showing that if the star was massive enough it would form what was much later called a "black hole," where nothing could falling into the star, including light, could escape.
Physicists reacted to the Schwarzchild singularity just as anyone reacts to something which violates his fundamental beliefs and expectations. First was "this must be a mistake in the derivation." Then, "the derivation is fine, but it can't happen in nature." Still later, "it can happen under General Relativity alone, but surely quantum mechanics will prevent the singularity." There was worse to come, too. It was soon realized that the Schwarzschild singularity wasn't the only thing happening at black hole -- matter falling into the hole not only can't escape, but it continues to fall into the very center of the black hole, forming a real "singularity" where the density of matter must be infinite.
Thorne then recounts the history of the study of "the problem of gravitational collapse." beginning with the work of the Indian astrophysicist, Subrahmanyan Chandrasekhar, who showed that large burned out stars must collapse into something. Next was the Russian physicist Lev Davidovich Landau, who, while fighting deportation to the Gulag, showed that neutron stars were one possible final state. Finally, in 1939, the American physicist Robert Oppenheimer showed that some stars are too big to form a stable neutron star. Did this mean black holes must form? Perhaps not. John Archibald Wheeler, the astrophysicist who later coined the phrase "black hole", originally believed that a large star would eject most its mass before the final collapse, preventing the formation of a black hole, or that "the fiery marriage of gravitation and quantum mechanics" would stop the collapse. Finally, in the early 1960s, computer simulations by Wheeler's group showed that very large dead stars must collapse into a black hole. Thus, fifty years after Einstein and Schwarzschild, it was shown that black holes were not only allowed, but must form on the death of very large stars.
The middle part of the book also contains a history of the Manhattan Project to build the first atomic bomb. This was the defining event of 20th century physics, as it brought together nearly every physicist in the western world. The Project, in addition to fostering cooperative research in other fields (including general relativity), also showed the need for the development of large electronic computers, which would later become important for solving the complicated equations of general relativity. Thorne also describes the chain of events that lead to Oppenheimer loosing his security clearance and hence permission to work in weapons research.
The later part of the book is devoted to Thorne's own work, especially his work on "closed time-like loops", a polite way of saying "time machines", which are allowed under general relativity if one postulates the existence of "exotic matter". Interestingly enough, Thorne seems to believe that quantum mechanics will prevent us from building time machines. This is much like the view of his mentor Wheeler, who believed that something would stop the formation of black holes. So far, every prediction of general relativity has held up. It remains to be seen if Einstein's latest "outrageous legacy" will also stand the test of time.
Author: Kip S. Thorne, Ph.D. Title: Black Holes & Time Warps: Einstein's Outrageous Legacy Publisher: W. W. Norton & Company, Inc., New York (1994) ISBN: 0-393-03505-0 List Price: $30.00
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© 1996 by Michael J. Mehl
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