Black Holes and Time Warps: Einstein’s Outrageous Legacy

605 Pages·1995·9.99 MB·English

by  Kip S. Thorne

BLACK HOLES
AND
TIME WARPS

Einstein’s 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
The Commonwealth Fund Book Program
gratefully acknowledges the assistance
of The Rockefeller University in the
administration of the program
I dedicate this book to
JOHN ARCHIBALD WHEELER,
my mentor and friend.
Contents
Foreword by Stephen Hawking
Introduction by Frederick Seitz
Preface
what this book is about, and how to read it
Prologue: A Voyage among the Holes
in which the reader, in a science fiction tale, encounters black holes
and all their strange properties as best we understand them in the
1990s 1. The Relativity of Space and Time
in which Einstein destroys Newton’s conceptions of space and time
as Absolute 2. The Warping of Space and Time
in which Hermann Minkowski unifies space and time, and Einstein
warps them 3. Black Holes Discovered and Rejected
in which Einstein’s laws of warped spacetime predict black holes,
and Einstein rejects the prediction 4. The Mystery of the White
Dwarfs
in which Eddington and Chandrasekhar do battle over the deaths of
massive stars; must they shrink when they die, creating black
holes? or will quantum mechanics save them?
5. Implosion Is Compulsory
in which even the nuclear force, supposedly the strongest of all
forces, cannot resist the crush of gravity 6. Implosion to What?
in which all the armaments of theoretical physics cannot ward off
the conclusion: implosion produces black holes 7. The Golden Age
in which black holes are found to spin and pulsate, store energy
and release it, and have no hair 8. The Search
in which a method to search for black holes in the sky is proposed
and pursued and succeeds (probably) 9. Serendipity
in which astronomers are forced to conclude, without any prior
predictions, that black holes a millionfold heavier than the Sun
inhabit the cores of galaxies (probably) 10. Ripples of Curvature
in which gravitational waves carry to Earth encoded symphonies of
black holes colliding, and physicists devise instruments to monitor
the waves and decipher their symphonies 11. What Is Reality?
in which spacetime is viewed as curved on Sundays and flat on
Mondays, and horizons are made from vacuum on Sundays and
charge on Mondays, but Sundays experiments and Monday’s
experiments agree in all details 12. Black Holes Evaporate
in which a black-hole horizon is clothed in an atmosphere of
radiation and hot particles that slowly evaporate, and the hole
shrinks and then explodes 13. Inside Black Holes
in which physicists, wrestling with Einstein s equation, seek the
secret of what is inside a black hole: a route into another universe?
a singularity with infinite tidal gravity? the end of space and time,
and birth of quantum foam?
14. Wormholes and Time Machines
in which the author seeks insight into physical laws by asking: can
highly advanced civilizations build wormholes through hyperspace
for rapid interstellar travel and machines for traveling backward in
time?
Epilogue
an overview of Einstein’s legacy, past and future, and an update on
several central characters Acknowledgments
my debts of gratitude to friends and colleagues who influenced this
book Characters
a list of characters who appear significantly at several different
places in the book Chronology
a chronology of events, insights, and discoveries
Glossary
definitions of exotic terms
Notes
what makes me confident of what I say?
Bibliography
People Index
Subject Index
Foreword
T
his book is about a revolution in our view of space and time, and its
remarkable consequences, some of which are still being unraveled. It is also a
fascinating account, written by someone closely involved, of the struggles and
eventual success in a search for an understanding of what are possibly the most
mysterious objects in the Universe-black holes.
It used to be thought obvious that the surface of the Earth was flat: It either
went on forever or it had some rim that you might fall over if you were foolish
enough to travel too far. The safe return of Magellan and other round-the-world
travelers finally convinced people that the Earth’s surface was curved back on
itself into a sphere, but it was still thought self-evident this sphere existed in a
space that was flat in the sense that the rules of Euclid’s geometry were obeyed:
Parallel lines never meet. However, in 1915 Einstein put forward a theory that
combined space and time into something called spacetime. This was not flat but
curved or warped by the matter and energy in it. Because spacetime is very
nearly flat in our neighborhood, this curvature makes very little difference in
normal situations. But the implications for the further reaches of the Universe
were more surprising than even Einstein ever realized. One of these was the
possibility that stars could collapse under their own gravity until the space
around them became so curved that they cut themselves off from the rest of the
Universe. Einstein himself didn’t believe that such a collapse could ever occur,
but a number of other people showed it was an inevitable consequence of his
theory.
The story of how they did so, and how they found the peculiar properties of
the black holes in space that were left behind, is the subject of this book. It is a
history of scientific discovery in the making, written by one of the participants,
rather like The Double Helix by James Watson about the discovery of the
structure of DNA, which led to the understanding of the genetic code. But unlike
the case of DNA, there were no experimental results to guide the investigators.
Instead, the theory of black holes was developed before there was any indication
from observations that they actually existed. I do not know any other example in
science where such a great extrapolation was successfully made solely on the
basis of thought. It shows the remarkable power and depth of Einstein’s theory.
There is much we still don’t know, such as what happens to objects and
information that fall into a black hole. Do they reemerge elsewhere in the
Universe, or in another universe? And can we warp space and time so much that
one can travel back in time? These questions are part of our ongoing quest to
understand the Universe. Maybe someone will come back from the future and
tell us the answers.
STEPHEN HAWKING
Introduction
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 hole—a
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 hole’s “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 Einstein’s 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