Time's Arrows Today: Recent Physical and Philosophical Work on the Direction of Time

345 Pages·1997·8.25 MB·English

by  Steven F. Savitt

While it seems manifest in our experience that time flows - from the past, to
the present moment and into the future, there are a number of philosophical
and physical objections to this. In the quest to make sense of this conundrum
philosophers and physicists confront fascinating and irresistible questions
such as: Can effects precede causes? Can one travel in time? Can the expan-
sion of the universe or the process of measurement in quantum mechanics
provide a direction of time?
In this book eleven eminent scholars, standing at the boundary between
physics and philosophy, attempt to answer these questions in an entertain-
ing yet rigorous way. For example, William Unruh's chapter is one of the
first non-technical essays by this important cosmologist. Philip Stamp and
Anthony Leggett discuss macroscopic quantum phenomena, a subject
which has not been discussed much outside the specialist literature. John
Earman's chapter on time travel is likely to become one of the landmarks
in the literature.
The book will be enjoyed by anyone of a speculative turn of mind fasci-
nated by the puzzle of time.

Time's Arrows Today

Time's Arrows Today
Recent physical and philosophical work on the
direction of time
Edited by Steven F Savitt
University of British Columbia
CAMBRIDGE
UNIVERSITY PRESS
CAMBRIDGE UNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao Paulo
Cambridge University Press
The Edinburgh Building, Cambridge CB2 2RU, UK
Published in the United States of America by Cambridge University Press, New York
www. Cambridge. org
Information on this title: www.cambridge.org/9780521461115
© Cambridge University Press 1995
This publication is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without
the written permission of Cambridge University Press.
First published 1995
Reprinted 1998
A catalogue record for this publication is available from the British Library
ISBN-13 978-0-521-46111-5 hardback
ISBN-10 0-521-46111-1 hardback
ISBN-13 978-0-521-59945-0 paperback
ISBN-10 0-521-59945-8 paperback
Transferred to digital printing 2005
Contents
Preface ix
Notes on the contributors x
Introduction 1
PART l Cosmology and time's arrow
1 Time, gravity, and quantum mechanics 23
WILLIAM UNRUH, Physics: UBC
2 Cosmology, time's arrow, and that old double standard 66
HUW PRICE, Philosophy: Sydney
PART 2 Quantum theory and time's arrow
3 Time's arrow and the quantum measurement problem 97
ANTHONY LEGGETT, Physics: Urbana-Champaign
4 Time, decoherence, and 'reversible' measurements 107
PHILIP STAMP, Physics: UBC
5 Time flow, non-locality, and measurement in quantum 155
mechanics
STORRS McCALL, Philosophy: McGill
6 Stochastically branching spacetime topology 173
ROY DOUGLAS, Mathematics: UBC
PART 3 Thermodynamics and time's arrow
7 The elusive object of desire: in pursuit of the kinetic 191
equations and the Second Law
LAWRENCE SKLAR, Philosophy: Michigan
8 Time in experience and in theoretical description of the 217
world
LAWRENCE SKLAR, Philosophy: Michigan
VU
Contents
9 When and why does entropy increase? 230
MARTIN BARRETT & ELLIOTT SOBER, Philosophy: Wisconsin
PART 4 Time travel and time's arrow
10 Closed causal chains 259
PAUL HORWICH, Philosophy: MIT
11 Recent work on time travel 268
JOHN E ARM AN, History and Philosophy of Science: Pittsburgh
References 311
Index 325
Vlll
Preface
Most of the contributors to this volume are philosophers of science, but three are
physicists (Leggett, Stamp, and Unruh) and one is a mathematician (Douglas).
Their chapters are intended to be original contributions towards answers to,
rather than comprehensive discussions of, some of the oddly exasperating and
fascinating questions known collectively as the problem of the direction of
time, but the chapters were written with an eye towards communicating their
results to the scientifically literate non-specialist.
Most of the work in this volume was presented at the Time's Arrows Today'
Conference held on the campus of the University of British Columbia in June,
1992. The exceptions are the papers by Douglas and Earman and Sklar's The
elusive object of desire: in pursuit of the kinetic equations and the Second Law'.
I am grateful to the Social Sciences and Humanities Research Council of
Canada and to the Dean of the Faculty of Arts and the President of the Univer-
sity of British Columbia for their generous support of that conference.
In addition I wish to express my gratitude to Philip Stamp, whose advice and
assistance have been invaluable, to Roy Douglas, who has long provided for me
a model of rigorous thinking, and to William Unruh, without whose help my
discussion of Penrose's thought experiment in the Introduction would have
been much easier to write.
Steven F. Savitt
Vancouver, British Columbia