Five Billion Years of Solitude: The Search for Life Among the Stars

244 Pages·2013·2.82 MB·English

by  Lee Billings

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First published by Current, a member of Penguin Group (USA) LLC, 2013
Copyright © 2013 by Lee Billings
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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