THE GREAT SILENCE the Science and Philosophy of Fermi's
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The Great Silence THE GREAT SILENCE The Science and Philosophy of Fermi’s Paradox milan m. ćirković 1 1 Great Clarendon Street, Oxford, OX2 6DP, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries © Milan M. Ćirković 2018 The moral rights of the author have been asserted First Edition published in 2018 Impression: 1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America British Library Cataloguing in Publication Data Data available Library of Congress Control Number: 2017954178 ISBN 978–0–19–964630–2 Printed and bound by CPI Group (UK) Ltd, Croydon, CR0 4YY Links to third party websites are provided by Oxford in good faith and for information only. Oxford disclaims any responsibility for the materials contained in any third party website referenced in this work. To Jelena Dimitrijević, Who reads by flashlight and time-travels in libraries, with kittens How many kingdoms know us not! Blaise Pascal The void is the only great wonder of the world. René Magritte Man is a very small thing, and the night is very large and full of wonders. Lord Dunsany Every classification throws light on something. Sir Isaiah Berlin CONTENTS Introductory Note xiii Acknowledgements xxv 1. Introduction: The Many Faces of Fermi’s Paradox 1 1.1 The Famous Lunch 1 1.2 Different Versions of the Paradox 4 1.3 Spatio-Temporal Scales and the Real Strength of StrongFP 13 1.4 Structure (and Culture) of Fermi’s Paradox 19 1.5 Philosophical Assumptions 21 1.6 The Null Hypothesis 27 1.7 Why Now? 31 1.8 Two Is Equal to One: Fermi’s Paradox and the Success of SETI 36 1.9 X-Factors and Navigating Spaceship Earth 40 2. ‘What’s Past Is Prologue’: Cosmological and Astrophysical Background 43 2.1 The New Standard Cosmological Model 45 2.2 The Size and Age of the Galaxy 48 2.3 The Galactic Habitable Zone 52 2.4 Horizons and Temporal Scales 61 3. Speaking Prose: Realism, Naturalism, Copernicanism, Non-Exclusivity 69 3.1 Why Philosophy? 69 3.2 Philosophical Naturalism 74 3.3 Scientific Realism 77 3.4 Copernicanism 78 3.5 Gradualism (and Red Herrings) 81 3.6 The Non-Exclusivity Principle 85 3.7 The Continuity Thesis 91 3.8 Postbiological Evolution 92 x | CONTENTS 3.9 The Drake Equation, for Good or Bad 95 3.10 Let the Games Begin! 99 4. L’Année dernière à Marienbad: Solipsist Solutions 101 4.1 Down with Realism! 103 4.2 Saucers, Utensils, and Other UFOs 109 4.3 Special Creation 113 4.4 Zoos, Interdicts, Dogs, and the Mind of Newton 115 4.5 Living in a Planetarium—or a SimCity 120 4.6 Directed Panspermia: Are We the Aliens? 127 4.7 A New Cosmogony? 133 4.8 A Solipsist Résumé 137 5. Terra Nostra: ‘Rare Earth’ and Related Solutions 143 5.1 Down with Copernicanism! 145 5.2 Modern Rare-Earth Hypotheses 152 5.3 Gaia or Bust? 156 5.4 An Adaptationist Solution? 159 5.5 Unphysical Ceteris Paribus, and Other Problems 165 5.6 A Rare-Earthist Résumé 167 6. At the Mountains of Madness: Neocatastrophic Solutions 169 6.1 Down with Gradualism! 170 6.2 Natural Hazards I: Random Delays 172 6.3 Natural Hazards II: Synchronized Delays 174 6.4 Intentional Hazards I: Self-Destruction 179 6.5 Intentional Hazards II: Self-Limitation 182 6.6 Intentional Hazards III: Deadly Probes and Unstable Equilibria 187 6.7 Transcendence, Transcension, and Related Scenarios 196 6.8 A Neocatastrophist Résumé 199 7. The Cities of the Red Night: Logistic Solutions 203 7.1 Down with ‘-Ism’! 205 7.2 Wrong Tree? 210 7.3 Persistence 212 7.4 Migrations: To the Galactic Rim and Beyond 215 7.5 Sustainability 220 7.6 Metabolic Problems and Digital Indulgence 222 7.7 A Logistic Résumé 228 8. The Tournament: How To Rate Solutions and Avoid Exclusivity 231 8.1 A Table Too Large? 232 8.2 Manifestations, Artefacts, and Detectability 238 8.3 No Small Prices To Pay? 251 8.4 The ‘Great Filter’ Redux 259 CONTENTS | xi 9. The Last Challenge For Copernicanism? 263 9.1 Copernicanism Once Again 268 9.2 The Importance of Being Postbiological 275 9.3 Radical Departures: Distributed Computing, StarUniverse Maker, and the New Cosmogony Revisited 279 9.4 Fermi’s Paradox as a Successful Provocation 282 9.5 The Failure of Conventional SETI as a Philosophical Failure 285 Endnotes 291 References 341 Index 391 INTRODUCTORY NOTE he perennial question Are we alone? is one of those crucial watersheds in human quest for understanding the universe which defy both simple digests and simple answers. One of its deepest components is the puzzle Talmost universally—though imprecisely—known as Fermi’s paradox, the absence of extraterrestrial life and its manifestations from our vicinity in both space and time. Originating in lunchtime remarks of the great physicist Enrico Fermi in 1950 (although some precursors have been noted), the chestnut has proven to be one of the deepest, subtlest, and most persistent challenges in the history of science. This book is, at least in part, devoted to justifying such a sweeping claim. But there is much more, even beyond the borders of science: Fermi’s problem not only shaped innumerable science-fiction visions, but also profoundly influenced all our thinking about the relationship of the cosmos and the mind, as well as about the future of humanity and cognition. Encapsulated in the legendary question Where is everybody?, the puzzle turned out to be a tough nut to crack. Even a cursory look at the literature will show that, since about 1975, the number of publications containing references to Fermi’s paradox is well in the hundreds. Still, the problem remains completely and irritatingly unsolved. The present book grew from a profound dissatisfaction I have felt for quite some time that people do not take Fermi’s paradox seriously enough, in spite of the multiple recent discoveries and trends which make the problem objectively more disturbing than ever. As one example among many, in Fermi’s time, no data on the age distribution of habitable planets and their parent stars were available, and one could plausibly argue—as with the ‘rare-Earth’ claims of some modern researchers—that Earth is in the extreme early tail of this age distribution, being among the oldest, if not the oldest habitable planet in the Milky Way. This would, in turn, mean that all other biospheres are younger xiv | INTRODUCTORY NOTE than the terrestrial one and, as long as the emergence of intelligent beings and their civilizations follows the terrestrial chronology even roughly, that we must be the oldest civilized species in the Galaxy. Fermi’s paradox is then, obviously, resolved, since nobody is around yet. The contemporary ‘astrobiological revolu- tion’ brought about a revolutionary change in this respect: since 2001 and the seminal results of Charles Lineweaver, we are aware that Earth is, in fact, a latecomer on the Galactic scene: the formation of Earth-like planets started more than 9 Ga (a giga-annus = 1 billion years = 109 years) before the birth of Earth and the Solar System, and reached its peak at −6.2 ± 0.7) Ga, still some 1.7 ± 0.7 Ga before our planet completed its original accretion.1 That, obviously, means that most of the habitable sites in the Milky Way are billions of years older and, if we accept the straightforward Copernican assumption, so must be intelligent beings which have evolved on these sites. So, indeed, where is every body? This book is about many facets of one particular problem belonging to astro- biology and, more specifically, to its subfield dealing with the Search for Extra- Terrestrial Intelligence (SETI). SETI is, contrary to the popular impression, a very large field when the size is gauged not by the funds invested or the number of people involved, but by the scope of the research topics and the relevance of its questions. Thus, the reader will find the amount of general SETI content somewhat disappointing; fortunately, there are multiple high-quality introduc- tions and reviews of the entire field, some of which are cited in the endnotes.2 So, although I may mention some other important problems of SETI studies (e.g. target selection, wavelength choice, or even whether it is safe to transmit our messages) in passing, there is no way justice could be given to them in such a brief format. The Drake equation will not be discussed in detail either, but for an entirely different reason, explained in Chapter 3: while its historical role has been undisputed, the continuation of its use in the present epoch of the astro- biological revolution is, in my view, not only outdated, but can be counterpro- ductive and supply ammunition to the ‘fundamentalist’ opponents of the whole endeavour.3 Fermi’s paradox touches upon many issues belonging to various traditional disciplines; it is enough to look into items commonly used in formulations (such as those given in Section 1.2) of the paradox: the Galaxy, intelligence, civ- ilization, technology, evolution, interstellar travel, ages, manifestations, detec- tion, naturalism, cosmological horizon, and so on.