Black Holes and Baby Universes
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Black Holes and Baby Universes and other essays by Stephen Hawking. Chapter 10 The Quantum Mechanics of Black Holes The 1st 30 years of this Century saw the emergence of three theories that radically altered man's view of physics and of reality itself. Physicists are still trying to explore their implications and to fit them together. The three theories are the special theory of relativity 1905 The general theory of relativity 1915 In the theory of quantum mechanics, circa 1926 Albert Einstein was largely responsible for the first, was entirely responsible for the second and played a major role in the development of the third. Yet Einstein never accepted quantum mechanics because of its element of chance and uncertainty. His feelings were summed up in his oft quoted statement. God does not play dice. Most physicists, however, readily accepted both special relativity and quantum mechanics because they described effects that could be directly observed. General relativity, on the other hand, was largely ignored because it seemed too complicated. Mathematically was not testable in the laboratory and was a purely classical theory that did not seem compatible with quantum mechanics. Thus, general relativity remained in the doldrums for nearly 50 years. The great extension of astronomical observations that began early in the 19 sixties brought about a revival of interest in the classical theory of general relativity because it seemed that many of the new phenomena that were being discovered, such as quasars, pulsars and compact X ray sources indicated the existence of very strong gravitational fields, fields that could be described Onley by general relativity. Quasars are star like objects that must be many times brighter than entire Galaxies. If they are as distant as the reddening of their spectra indicates. Pulsars are the rapidly blinking remnants of supernova explosions believed to be ultra dense neutron stars. Compact X ray sources revealed by instruments aboard space vehicles may also be neutron stars or maybe hypothetical objects of still higher density, namely black holes. One of the problems facing physicists who sought to apply general relativity to these newly discovered or hypothetical objects was to make it compatible with quantum mechanics. Within the past few years, there have been developments that could give rise to the hope that before too long we shall have a fully consistent quantum theory of gravity, one that will agree with general relativity for macroscopic objects and will, one hopes, be free of the mathematical infinities that have long bedeviled other quantum field theories? These developments have to do with certain recently discovered quantum effects associated with black holes, which provide a remarkable connection between black holes and the laws of thermodynamics.