IF THE UNIVERSE IS TEEMING WITH ALIENS ... WHERE IS EVERYBODY? This page intentionally left blank IF THE UNIVERSE IS TEEMING WITH ALIENS ... WHERE IS EVERYBODY? FIFTY SOLUTIONS TO THE FERMI PARADOX AND THE PROBLEM OF EXTRATERRESTRIAL LIFE Stephen Webb Copernicus Books IN ASSOCIATION WITH Praxis Publishing Ltd. An Imprint of Springer-Verlag © Praxis Publishing Ltd, 2002. 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, electronic, mechanical, photocopying, recording, or other- wise, without the prior written permission of the publisher. Published in the United States by Copernicus Books, an imprint of Springer-Verlag New York, Inc. A member of BertelsmannSpringer Science+Business Media GmbH Copernicus Books 37 East 7th Street New York, NY 10003 www.copernicusbooks.com Library of Congress Cataloging-in-Publication Data Webb, Stephen. If the universe is teeming with aliens . where is everybody? : fifty solutions to the Fermi paradox and the problem of extraterrestrial life / Stephen Webb. p. cm. Includes bibliographical references and index. ISBN 0-387-95501-1 (acid-free paper) 1. Fermi paradox. 2. Life on other planets. 3. Fermi, Enrico, 1901–1945. I. Title. QB54.W384 2002 576.8’39—dc21 2002073910 Manufactured in the United States of America. Printed on acid-free paper. 987654321 ISBN 0-387-95501-1 SPIN 10879967 To Heike This page intentionally left blank CONTENTS Preface ix Figure Credits xi Chapter 1 Where Is Everybody? 1 Chapter 2 Of Fermi and Paradox 7 Enrico Fermi 8 Paradox 12 The Fermi Paradox 17 Chapter 3 They Are Here 27 SOLUTION 1 They Are Here and They Call Themselves Hungarians 28 SOLUTION 2 They Are Here and Are Meddling in Human Affairs 29 SOLUTION 3 They Were Here and Left Evidence of Their Presence 33 SOLUTION 4 They Exist and They Are Us — We Are All Aliens! 44 SOLUTION 5 The Zoo Scenario 46 SOLUTION 6 The Interdict Scenario 49 SOLUTION 7 The Planetarium Hypothesis 51 SOLUTION 8 God Exists 55 Chapter 4 They Exist But Have Not Yet Communicated 61 SOLUTION 9 The Stars Are Far Away 62 SOLUTION 10 They Have Not Had Time to Reach Us 72 SOLUTION 11 A Percolation Theory Approach 74 SOLUTION 12 Bracewell–von Neumann Probes 79 SOLUTION 13 We Are Solar Chauvinists 84 SOLUTION 14 They Stay at Home... 85 SOLUTION 15 ...and Surf the Net 86 SOLUTION 16 They Are Signaling But We Do Not Know How to Listen 88 SOLUTION 17 They Are Signaling But We Do Not Know at Which Frequency to Listen 94 SOLUTION 18 Our Search Strategy Is Wrong 102 SOLUTION 19 The Signal Is Already There in the Data 105 SOLUTION 20 We Have Not Listened Long Enough 106 SOLUTION 21 Everyone Is Listening, No One Is Transmitting 108 SOLUTION 22 Berserkers 111 SOLUTION 23 They Have No Desire to Communicate 113 SOLUTION 24 They Develop a Different Mathematics 116 SOLUTION 25 They Are Calling But We Do Not Recognize the Signal 118 SOLUTION 26 They Are Somewhere But the Universe Is Stranger Than We Imagine 121 SOLUTION 27 A Choice of Catastrophes 122 SOLUTION 28 They Hit the Singularity 134 SOLUTION 29 Cloudy Skies Are Common 137 SOLUTION 30 Infinitely Many ETCs Exist But Only One Within Our Particle Horizon: Us 138 Chapter 5 They Do Not Exist 141 SOLUTION 31 The Universe Is Here for Us 143 SOLUTION 32 Life Can Have Emerged Only Recently 147 SOLUTION 33 Planetary Systems Are Rare 150 SOLUTION 34 We Are the First 153 SOLUTION 35 Rocky Planets Are Rare 156 SOLUTION 36 Continuously Habitable Zones Are Narrow 158 SOLUTION 37 Jupiters Are Rare 160 SOLUTION 38 Earth Has an Optimal “Pump of Evolution” 164 SOLUTION 39 The Galaxy Is a Dangerous Place 166 SOLUTION 40 A Planetary System Is a Dangerous Place 172 SOLUTION 41 Earth’s System of Plate Tectonics Is Unique 180 SOLUTION 42 The Moon Is Unique 184 SOLUTION 43 Life’s Genesis Is Rare 189 SOLUTION 44 The Prokaryote–Eukaryote Transition Is Rare 206 SOLUTION 45 Toolmaking Species Are Rare 211 SOLUTION 46 Technological Progress Is Not Inevitable 215 SOLUTION 47 Intelligence at the Human Level Is Rare 217 SOLUTION 48 Language Is Unique to Humans 223 SOLUTION 49 Science Is Not Inevitable 231 Chapter 6 Conclusion 233 SOLUTION 50 The Fermi Paradox Resolved . 234 Chapter 7 Notes and Further Reading 241 Chapter 8 References 275 Index 283 PREFACE This book is about the Fermi paradox — the contradiction between the apparent absence of aliens, and the common expectation that we should see evidence of their existence. I was fascinated by the paradox when I first met it some 17 years ago, and it fascinates me still. Over those years, many authors (too many to mention here, though their names appear in the ref- erence list at the back of this book) have enthralled me with their writing about the paradox. Their influence upon this work will be clear. I have also discussed the paradox with many friends and colleagues; although they are too numerous to mention individually, I am indebted to them all. Several people have contributed directly to the writing of this book, and I would like to take this chance to thank them. Clive Horwood of Praxis Publishing, John Watson of Springer-Verlag and Paul Farrell of Copernicus Books have been very supportive of the project; the book would not have been completed had it not been for their advice and encouragement. (I would also like to thank John for sharing his favored resolution of the paradox over an enjoyable working lunch.) Stuart Clark provided many useful comments on an early draft of the manuscript; Bob Marriott and Timothy Yohn caught several errors and solecisms in a later draft (Bob also sent me a list of 101 resolutions of the paradox — 75 of which I agree with); and I am extremely grateful to Steve Gillett for putting me right on many scientific points. (I am, of course, responsible for those errors that remain.) Mareike Paessler was an exceptionally observant and helpful Production Editor. Her painstaking work with Assistant Editor Anna Painter improved the text enormously. Several authors and organizations kindly gave permission to reproduce figures; I am particularly grateful to thank Lora Gordon, Geoffrey Landis, Ian Wall, Susan Lendroth, Reinhard Rachel, Heather Lindsay and Merrideth Miller for help in obtaining suitable figures. Paul Bell gently corrected my misidentification of Feynman in Figure 28, and shared some inter- esting ideas on the paradox. I would like to thank David Glasper for sharing his recollections of a childhood incident that affected us both. Finally, of course, I would like to thank my family — Heike, Ron, Ronnie, Peter, Jackie, Emily and Abigail — for their patience. I spent time writing that I should instead have shared with them. Stephen Webb Milton Keynes, July 2002 ix This page intentionally left blank FIGURE CREDITS I would like to acknowledge the following sources and copyright hold- ers for granting permission to use their images. Figures 1, 6, 7, 8, 10 and 28 are courtesy of the American Institute of Physics Emilio Segré Visual Archives. Figure 5 is © The New Yorker Collection 1950 Alan Dunn from cartoonbank.com. All Rights Reserved. Both Figures 9 and 29 are seti League photographs, used by permission. Figures 13, 15–19, 21, 22, 44–46, 48–52, 57–60 and 70 are courtesy of nasa. Figure 14 is courtesy of the Astronomical Society of the Pacific. Figure 20 is courtesy of Radford University and Lora Gordon. Figure 23 is courtesy of Michael Carroll and the Planetary Organisation. Figure 25 is courtesy of IoP and Miguel Alcubierre Moya. Figure 27 is courtesy of Geoffrey Landis. Figure 30 is courtesy of ligo. Figure 31 is courtesy of Antares – F. Montanet ccpm/in2p3/cnrs – Université Mediterranée. Figures 33 and 34 are both courtesy of the seti Institute, used by permission. Figure 40 is courtesy of Michael Daly, Uniformed Services University of the Health Sciences. Figure 41 is courtesy of cern. Figure 43 is © Frederik Ramm (see http://www.remote.org/frederik/culture/berlin/). Figure 53 is courtesy of nasa/P. J. T. Leonard, and Figure 54 is cour- tesy of nasa/Don Davis. Figure 55 is courtesy of noaa; photographer Michael Van Woert. Figure 56 is courtesy of noaa. The four images in Figure 62 are courtesy of Prof. Dr. K. O. Stetter and Dr. R. Rachel, Universität Regensburg, Mikrobiologie; © University of Regensburg. Figure 64 is courtesy of the Wellcome Trust. Figure 67 is © US Department of Energy Human Genome Project. Figure 69 is © Arizona State University, photograph by Alan Riggs. Figure 71 is courtesy of Creswell Crags, © Creswell Heritage Trust. xi This page intentionally left blank 1 Where Is Everybody? here is something beguiling about paradox. The impossible and paradoxical prints of Maurits Escher never fail to deceive the eye. TPoems like Robert Graves’ Warning to Children, which play with the paradox of infinite regress, make the head spin. Paradox lies at the heart of Joseph Heller’s Catch-22, one of the 20th century’s greatest novels. My favorite paradox, though, is that of Fermi. I first came across the Fermi paradox in the summer of 1984. I had just graduated from Bristol University, and I should have spent the sum- mer months studying Aitchison and Hey’s Gauge Theories in Particle Physics — required reading before I started postgraduate studies at Manchester University. Instead, I spent my time enjoying the sunshine on the Bristol Downs, studying my favorite reading matter: Isaac Asimov’s Science Fiction Magazine. (As with many people, SF sparked my interest in science.