Kip S. Thorne - Black Holes and Time Warps: Einstein’s Outrageous Legacy

The Commonwealth Fund Book Program
gratefully acknowledges the assistance
of The Rockefeller University in the
administration of the program

Copyright 1994 by Kip S. Thorne

All rights reserved

Book design by Jacques Chazaud.

Illustrations by Matthew Zimet.

The Library of Congress has cataloged the printed edition as follows:

Thorne, Kip S.

From black holes to time warps: Einsteins outrageous legacy / Kip S. Thorne.

p. cm.

Includes bibliographical references.

1. Physics-Philosophy. 2. Relativity (Physics) 3. Astrophysics. 4. Black holes (Astronomy)

I. Title.

QC6.T5261993

530.11dc20 93-2014

ISBN 978-0-393-31276-8

ISBN 0-393-31276-3

ISBN 978-0-393-24747-3 (e-book)

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BLACK HOLES
AND
TIME WARPS

Einsteins Outrageous Legacy

KIP S. THORNE

THE FEYNMAN PROFESSOR OF THEORETICAL PHYSICS
CALIFORNIA INSTITUTE OF TECHNOLOGY

A volume of

THE COMMONWEALTH FUND BOOK PROGRAM

under the editorship of Lewis Thomas, MD.

W W NORTON & COMPANY

New York London

I dedicate this book to
JOHN ARCHIBALD WHEELER,
my mentor and friend.

T his book is based upon a combination of firmly established physical principles and highly imaginative speculation, in which the author attempts to reach beyond what is solidly known at present and project into a part of the physical world that has no known counterpart in our everyday life on Earth. His goal is, among other things, to examine both the exterior and interior of a black holea stellar body so massive and concentrated that its gravitational field prevents material particles and light from escaping in ways which are common to a star such as our own Sun. The descriptions given of events that would be experienced if an observer were to approach such a black hole from outside are based upon predictions of the general theory of relativity in a strong-gravity realm where it has never yet been tested. The speculations which go beyond that and deal with the region inside what is termed the black holes horizon are based on a special form of courage, indeed of bravado, which Thorne and his international associates have in abundance and share with much pleasure. One is reminded of the quip made by a distinguished physicist, Cosmologists are usually wrong but seldom in doubt. One should read the book with two goals: to learn some hard facts with regard to strange but real features of our physical Universe, and to enjoy informed speculation about what may lie beyond what we know with reasonable certainty.

As a preface to the work, it should be said that Einsteins general theory of relativity, one of the greatest creations of speculative science, was formulated just over three-quarters of a century ago. Its triumphs in the early 1920s in providing an explanation of the deviations of the motion of the planet Mercury from the predictions of the Newtonian theory of gravitation, and later an explanation of the redshift of distant nebulas discovered by Hubble and his colleagues at Mount Wilson Observatory, were followed by a period of relative quiet while the community of physical scientists turned much of its attention to the exploitation of quantum mechanics, as well as to nuclear physics, high-energy particle physics, and advances in observational cosmology.

The concept of black holes had been proposed in a speculative way soon after the discovery of Newtons theory of gravitation. With proper alterations, it was found to have a natural place in the theory of relativity if one was willing to extrapolate solutions of the basic equations to such strong gravitational fields-a procedure which Einstein regarded with skepticism at the time. Using the theory, however, Chandrasekhar pointed out in 1930 that, according to it, stars having a mass above a critical value, the so-called Chandrasekhar limit, should collapse to become what we now call black holes, when they have exhausted the nuclear sources of energy responsible for their high temperature. Somewhat later in the 1930s, this work was expanded by Zwicky and by Oppenheimer and his colleagues, who demonstrated that there is a range of stellar mass in which one would expect the star to collapse instead to a state in which it consists of densely packed neutrons, the so-called neutron star. In either case, the final implosion of the star when its nuclear energy is exhausted should be accompanied by an immense outpouring of energy in a relatively short time, an outpouring to be associated with the brilliance of the supernovae seen occasionally in our own galaxy as well as in more distant nebulas.

World War II interrupted such work. However, in the 1950s and 1960s the scientific community returned to it with renewed interest and vigor on both the experimental and theoretical frontiers. Three major advances were made. First, the knowledge gained from research in nuclear and high-energy physics found a natural place in cosmological theory, providing support for what is commonly termed the big bang theory of the formation of our Universe. Many lines of evidence now support the view that our Universe as we know it originated as the result of expansion from a small primordial soup of hot, densely packed particles, commonly called a fireball. The primary event occurred at some time between ten and twenty billion years ago. Perhaps the most dramatic support for the hypothesis was the discovery of the degraded remnants of the light waves that accompanied a late phase of the initial explosion.

Second, the neutron stars predicted by Zwicky and the Oppenheimer team were actually observed and behaved much as the theory predicted, giving full credence to the concept that the supernovae are associated with stars that have undergone what may be called a final gravitational collapse. If neutron stars can exist for a given range of stellar mass, it is not unreasonable to conclude that black holes will be produced by more massive stars, granting that much of the observational evidence will be indirect. Indeed, there is much such indirect evidence at present.

Finally, several lines of evidence have given additional support to the validity of the general theory of relativity. They include high-precision measurements of spacecraft and planetary orbits in our solar system, and observations of the lensing action of some galaxies upon light that reaches us from sources beyond those galaxies. Then, more recently, there is good evidence of the loss of energy of motion of mutually orbiting massive binary stars as a result of the generation of gravitational waves, a major prediction of the theory. Such observations give one courage to believe the untested predictions of the general theory of relativity in the proximity of a black hole and open the path to further imaginative speculation of the type featured here.