bet made by Stephen Hawking and Kip Thorne

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A Brief History of Time by Stephen Hawking


Albert Einstein, Albert Michelson, anthropic principle, Arthur Eddington, bet made by Stephen Hawking and Kip Thorne, Brownian motion, cosmic microwave background, cosmological constant, dark matter, Edmond Halley, Ernest Rutherford, Henri Poincaré, Magellanic Cloud, Stephen Hawking

There are other models to explain Cygnus X-l that do not include a black hole, but they are all rather far-fetched. A black hole seems to be the only really natural explanation of the observations. Despite this, I had a bet with Kip Thorne of the California Institute of Technology that in fact Cygnus X-l does not contain a black hole! This was a form of insurance policy for me. I have done a lot of work on black holes, and it would all be wasted if it turned out that black holes do not exist. But in that case, I would have the consolation of winning my bet, which would bring me four years of the magazine Private Eye. In fact, although the situation with Cygnus X-l has not changed much since we made the bet in 1975, there is now so much other observational evidence in favor of black holes that I have conceded the bet.

This would offer great possibilities for travel in space and time, but unfortunately it seems that these solutions may all be highly unstable; the least disturbance, such as the presence of an astronaut, may change them so that the astronaut could not see the singularity until he hit it and his time came to an end. In other words, the singularity would always lie in his future and never in his past. The strong version of the cosmic censorship hypothesis states that in a realistic solution, the singularities would always lie either entirely in the future (like the singularities of gravitational collapse) or entirely in the past (like the big bang). I strongly believe in cosmic censorship so I bet Kip Thorne and John Preskill of Cal Tech that it would always hold. I lost the bet on a technicality because examples were produced of solutions with a singularity that was visible from a long way away. So I had to pay up, which according to the terms of the bet meant I had to clothe their nakedness. But I can claim a moral victory. The naked singularities were unstable: the least disturbance would cause them either to disappear or to be hidden behind an event horizon.

ALSO BY STEPHEN HAWKING A Briefer History of Time Black Holes and Baby Universes and Other Essays The Illustrated A Brief History of Time The Universe in a Nutshell The Grand Design FOR CHILDREN George’s Secret Key to the Universe (with Lucy Hawking) George’s Cosmic Treasure Hunt (with Lucy Hawking) A BRIEF HISTORY OF TIME A Bantam Book Publishing History Bantam illustrated hardcover edition published November 1996 Bantam hardcover edition/September 1998 Bantam trade paperback edition/September 1998 All rights reserved. Copyright © 1988, 1996 by Stephen Hawking Illustrations copyright © 1988 by Ron Miller BOOK DESIGN BY GLEN M. EDELSTEIN No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher.