Five Billion Years of Solitude: The Search for Life Among the Stars PDF
Preview Five Billion Years of Solitude: The Search for Life Among the Stars
CURRENT Published by the Penguin Group Penguin Group (USA) LLC 375 Hudson Street New York, New York 10014 USA | Canada | UK | Ireland | Australia | New Zealand | India | South Africa | China penguin.com A Penguin Random House Company First published by Current, a member of Penguin Group (USA) LLC, 2013 Copyright © 2013 by Lee Billings Penguin supports copyright. Copyright fuels creativity, encourages diverse voices, promotes free speech, and creates a vibrant culture. Thank you for buying an authorized edition of this book and for complying with copyright laws by not reproducing, scanning, or distributing any part of it in any form without permission. You are supporting writers and allowing Penguin to continue to publish books for every reader. LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA Billings, Lee, author. Five billion years of solitude : the search for life among the stars / Lee Billings. pages cm Includes bibliographical references and index. ISBN 978-0-698-13768-4 1. Life on other planets. 2. Extrasolar planets. I. Title. QB54.B54 22013 576.8'39—dc23 2013017672 While the author has made every effort to provide accurate telephone numbers, Internet addresses, and other contact information at the time of publication, neither the publisher nor the author assumes any responsibility for errors or for changes that occur after publication. Further, publisher does not have any control over and does not assume any responsibility for author or third-party Web sites or their content. To Mike and Pam, Bruce and Jo, Melissa, and all those with the courage to keep looking up Title Page Copyright Dedication Introduction CHAPTER 1 Looking for Longevity CHAPTER 2 Drake’s Orchids CHAPTER 3 A Fractured Empire CHAPTER 4 The Worth of a World CHAPTER 5 After the Gold Rush CHAPTER 6 The Big Picture CHAPTER 7 Out of Equilibrium CHAPTER 8 Aberrations of the Light CHAPTER 9 The Order of the Null CHAPTER 10 Into the Barren Lands Acknowledgments Selected Further Reading and Notes Index Here on Earth we live on a planet that is in orbit around the Sun. The Sun itself is a star that is on fire and will someday burn up, leaving our solar system uninhabitable. Therefore we must build a bridge to the stars, because as far as we know, we are the only sentient creatures in the entire universe. . . . We must not fail in this obligation we have to keep alive the only meaningful life we know of. –WERNHER VON BRAUN, ARCHITECT OF NASA’S APOLLO PROGRAM, AS RECALLED BY TOM WOLFE T his story properly begins 4.6 billion years ago, with the birth of our solar system from a cloud of cold hydrogen and dust several light-years wide. The cloud was but a wisp from a much larger mass of primordial gas, a stellar nursery manufacturing massive stars destined to explode as supernovae. One by one, the giant stars popped off like firecrackers, ejecting heavy elements that sizzled with radioactivity as they rode shock waves through the murk like so much scattered confetti. One of those enriching shock waves may have compressed the cloud, our cloud, in its passage. The cloud became dense enough for gravity to seize control, and it collapsed in on itself. Most of its material fell to its center to form a hot, simmering protostar. Eventually, the protostar gained enough mass to kindle a thermonuclear fire at its core, and the Sun began to shine. What was left of the cloud settled around the newborn star in a turbulent, spinning disk of incandescent vapor. Microscopic grains of metal, rock, ice, and tar rained out from the whirling disk as it slowly cooled. The grains swirled through the disk for millennia, occasionally colliding, sometimes sticking together, gradually glomming into ever-larger objects. First came millimeter-scale beads, then centimeter-scale pebbles, then meter-scale boulders, and finally kilometer-scale orbiting mountains called “planetesimals.” The planetesimals continued to collide, forming larger masses of ice, rock, and metal that grew with each impact. Within a million years, the planetesimals had grown into hundreds of Moon-size embryos, protoplanets that through violent collisions grew larger still, until they became full-fledged worlds. After perhaps one hundred million years of further collisions, the embryos in the inner solar system had combined to make Earth and the other rocky planets. The inner worlds were likely bone-dry, their water and other volatiles blowtorched away by the intense light of the newborn Sun. In the outer solar system, freezing temperatures locked the volatiles in ice. The ices provided more-solid construction material, allowing the cores of Jupiter and the other outer planets to rapidly form and sweep up lingering gas within the disk in only a few million years. As they grew, the giant planets created zones of instability where embryos could not assemble, leaving behind pockets of primordial planetesimals and bands of shattered rock and metal. These remnants are the asteroids. The giant planets also catapulted many icy planetesimals far out into the solar hinterlands, to drift in the dark out beyond the orbit of present-day Pluto. When jostled by perturbing planets, galactic tides, or close-passing stars, those icy outcasts fall back toward the Sun as comets. Finally, sometime between 3.8 and 4 billion years ago, a complex, chaotic, hazily understood series of gravitational interactions between the giant planets stirred up most of the outer solar system, sending barrages of asteroids and comets hurtling sunward to pound the dry, rocky inner worlds. This event is called the “Late Heavy Bombardment,” and was the last gasp of planet formation. We observe its effects in the cratered surface of the Moon, and also in
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