My grandfather, born before radio waves were even a laboratory curiosity, almost lived to see the first artificial satellite beeping down at us from space. There are people who were born before there was such a thing as an airplane, and who in old age saw four ships launched to the stars. For all our failings, despite our limitations and fallibilities, we humans are capable of greatness. This is true of our science and some areas of our technology, of our art, music, literature, altruism, and compassion, and even, on rare occasion, of our statecraft. What new wonders undreamt of in our time will we have wrought in another generation? And another? How far will our nomadic species have wandered by the end of the next century? And the next millennium?
Two billion years ago our ancestors were microbes; a halfbillion years ago, fish; a hundred million years ago, something like mice; ten million years ago, arboreal apes; and a million years ago, proto-humans puzzling out the taming of fire. Our evolutionary lineage is marked by mastery of change. In our time, the pace is quickening.
When we first venture to a near-Earth asteroid, we will have entered a habitat that may engage our species forever. The first voyage of men and women to Mars is the key step in transforming us into a multiplanet species. These events are as momentous as the colonization of the land by our amphibian ancestors and the descent from the trees by our primate ancestors.
Fish with rudimentary lungs and fins slightly adapted for walking must have died in great numbers before establishing a permanent foothold on the land. As the forests slowly receded, our upright apelike forebears often scurried back into the trees, fleeing the predators that stalked the savannahs. The transitions were painful, took millions of years, and were imperceptible to those involved. In our case the transition occupies only a few generations, and with only a handful of lives lost. The pace is so swift that we are still barely able to grasp what is happening.
Once the first children are born off Earth; once we have bases and homesteads on asteroids, comets, moons, and planets; once we're living off the land and bringing up new generations on other worlds, something will have changed forever in human history. But inhabiting other worlds does not imply abandoning this one, any more than the evolution of amphibians meant the end of fish. For a very long time only a small fraction of us will be out there.
"In modern Western society," writes the scholar Charles Lindholm,
the erosion of tradition and the collapse of accepted religious belief leaves us without a telos [an end to which we strive], a sanctified notion of humanity's potential. Bereft of a sacred project, we have only a demystified image of a frail and fallible humanity no longer capable of becoming god-like.
I believe it is healthy—indeed, essential—to keep our frailty and fallibility firmly in mind. I worry about people who aspire to be "god-like." But as for a long-term goal and a sacred project, there is one before us. On it the very survival of our species depends. If we have been locked and bolted into a prison of the self, here is an escape hatch—something worthy, something vastly larger than ourselves, a crucial act on behalf of humanity. Peopling other worlds unifies nations and ethnic groups, binds the generations, and requires us to be both smart and wise. It liberates our nature and, in part, returns us to our beginnings. Even now, this new telos is within our grasp.
The pioneering psychologist William James called religion a "feeling of being at home in the Universe." Our tendency has been, as I described in the early chapters of this book, to pretend that the Universe is how we wish our home would be, rather than to revise our notion of what's homey so it embraces the Universe. If, in considering James' definition, we mean the real Universe, then we have no true religion yet. That is for another time, when the sting of the Great Demotions is well behind us, when we are acclimatized to other worlds and they to us, when we are spreading outward to the stars.
The Cosmos extends, for all practical purposes, forever. After a brief sedentary hiatus, we are resuming our ancient nomadic way of life. Our remote descendants, safely arrayed on many worlds through the Solar System and beyond, will be unified by their common heritage, by their regard for their home planet, and by the knowledge that, whatever other life may be, the only humans in all the Universe come from Earth.
They will gaze up and strain to find the blue dot in their skies. They will love it no less for its obscurity and fragility. They will marvel at how vulnerable the repository of all our potential once was, how perilous our infancy, how humble our beginnings, how many rivers we had to cross before we found our way.
ABOUT THE AUTHOR
CARL SAGAN was the David Duncan Professor of Astronomy and Space Sciences and Director of the Laboratory for Planetary Studies at Cornell University. He played a leading role in the American space
program since its inception. He was a consultant and advisor to NASA since the 1950s, briefed the Apollo astronauts before their flights to the Moon, and was an experimenter on the Mariner, Viking, Voyager, and Galileo expeditions to the planets. He helped solve the mysteries of the high temperature of Venus (answer: massive greenhouse effect), the seasonal changes on Mars (answer: windblown dust), and the reddish haze of Titan (answer: complex organic molecules).
For his work, Dr. Sagan received the NASA medals for Exceptional Scientific Achievement and (twice) for Distinguished Public Service, as well as the NASA Apollo Achievement Award. Asteroid 2709 Sagan is named after him. He was also awarded the John F. Kennedy Astronautics Award of the American Astronautical Society, the Explorers Club 75th Anniversary Award, the Konstantin Tsiolkovsky Medal of the Soviet Cosmonauts Federation, and the Masursky Award of the American Astronomical Society ("for his extraordinary contributions to the development of planetary science .... As a scientist trained in both astronomy and biology, Dr. Sagan has made seminal contributions to the study of planetary atmospheres, planetary surfaces, the history of the Earth, and exobiology. Many of the most productive planetary scientists working today are his present and former students and associates").
ACKNOWLEDGMENTS
Most of the material in this book is new. A number of chapters have evolved from articles first published in Parade magazine, a supplement to the Sunday editions of American newspapers which, with an estimated 80 million readers, may be the most widely read magazine in the world. I am greatly indebted to Walter Anderson, the editor in chief, and David Currier, the executive editor, for their encouragement and editorial wisdom; and to the readers of Parade, whose letters have helped me understand where I have been clear, and where obscure, and how my arguments are received. Portions of other chapters have emerged from articles published in Issues in Science and Technology, Discover, The Planetary Report, Scientific American, and Popular Mechanics.
Aspects of this book have been discussed with a large number of friends and colleagues, whose comments have greatly improved it. Although there are too many to list by name, I would like to express my real gratitude to all of them. I want especially, though, to thank Norman Augustine, Roger Bonnet, Freeman Dyson, Louis Friedman, Everett Gibson, Daniel Goldin, J. Richard Gott III, Andrei Linde, Jon Lomberg, David Morrison, Roald Sagdeev, Steven Soter, Kip Throne, and Frederick Turner for their comments on all or part of the manuscript; Seth Kaufmann, Peter Thomas, and Joshua Grinspoon for their help with tables and graphs; and a brilliant array of astronomical artists, acknowledged at each illustration, who have permitted me to showcase some of their work. Through the generosity of Kathy Hoyt, Al McEwen, and Larry Soderblom, I've been able to display some of the exceptional photomosiacs, airbrush maps, and other reductions of NASA images accomplished at the Branch of Astrogeology, U.S. Geological Survey.
I am indebted to Andrea Barnett, Laurel Parker, Jennifer Bland, Loren Mooney, Karenn Gobrecht, Deborah Pearlstein, and the late Eleanor York for their able technical assistance; and to Harry Evans, Walter Weintz, Ann Godoff, Kathy Rosenbloom, Andy Carpenter, Martha Schwartz, and Alan MacRobert on the production end. Beth Tondreau is responsible for much of the design elegance on these pages.
On matters of space policy, I have benefited from discussions with other members of the board of directors of The Planetary Society, especially Bruce Murray, Louis Friedman, Norman Augustine, Joe Ryan, and the late Thomas O. Paine. Devoted to the exploration of the Solar System, the search for extraterrestrial life, and international missions by humans to other worlds, it is the organization that most nearly embodies the perspective of the present book.
Those readers interested in more information on this nonprofit organization, the largest space interest group on Earth, may contact:
THE PLANETARY SOCIETY
65 N. Catalina Avenue
Pasadena, CA 91106
Tel.: 1 800-9 WORLDS
As is true of every book I've written since 1977, I am more grateful than I can say to Ann Druyan for searching criticism and fundamental contributions both on content and style. In the vastness of space and the immensity of time, it is still my joy to share a planet and an epoch with Annie.
REFERENCES
(a few citations and suggestions for further reading)
PLANETARY EXPLORATION IN GENERAL:
J. Kelly Beatty and Andrew Chaiken, editors, The New Solar System, third edition (Cambridge: Cambridge
University Press, 1990).
Eric Chaisson and Steve McMillan, Astronomy Today (Englewood Cliffs, NJ: Prentice Hall, 1993).
Esther C. Goddard, editor, The Papers of Robert H. Goddard (New York: McGraw Hill, 1970) (three
volumes).
Ronald Greeley, Planetary Landscapes, second edition (New York: Chapman and Hall, 1994).
William J. Kaufmann III, Universe, fourth edition (New York: W. H. Freeman, 1993).
Harry Y. McSween, Jr., Stardust to Planets (New York: St. Martin's, 1994).
Ron Miller and William K. Hartmann, The Grand Tour: A Traveler's Guide to the Solar System, revised edition
(New York: Workman, 1993).
David Morrison, Exploring Planetary Worlds (New York: Scientific American Books, 1993).
Bruce C. Murray, journey to the Planets (New York: W.W. Norton, 1989).
Jay M. Pasachoff, Astronomy: From Earth to the Universe (New York: Saunders, 1993).
Carl Sagan, Cosmos (New York: Random House, 1980).
Konstantin Tsiolkovsky, The Call of the Cosmos (Moscow: Foreign Languages Publishing House, 1960) (English
translation).
CHAPTER 3, THE GREAT DEMOTIONS
John D. Barron and Frank J. Tipler, The Anthropic Cosmological Principle (New York: Oxford University Press,
1986).
A. Linde, Particle Physics and Inflationary Cosmology (Harwood Academy Publishers, 1991).
B. Stewart, "Science or Animism?," Creation /Evolution, vol. 12, no. 1 (1992), pp. 18 19.
Steven Weinberg, Dreams of a Final Theory (New York: Vintage Books, 1994).
CHAPTER 4, A UNIVERSE NOT MADE FOR US
Brian Appleyard, Understanding the Present: Science and the Soul of Modern Man (London: Picador/Pan Books
Ltd., 1992). Passages quoted appear, in order, on the following pages: 232, 27, 32, 19, 19, 27, 9, xiv, 137,
112 113, 206, 10, 239, 8, 8.
J. B. Bury, History of the Papacy in the 19th Century (New York: Schocken, 1964). Here, as in many other
sources, the 1864 Syllabus is transcribed into its "positive" form (e.g., "Divine revelation is perfect") rather
than as part of a list of condemned errors ("Divine revelation is imperfect").
CHAPTER 5, IS THERE INTELLIGENT LIFE ON EARTH?
Carl Sagan, W. R. Thompson, Robert Carlsson, Donald Gurnett, and Charles Hord, "A Search for Life on Earth
from the Galileo Spacecraft," Nature, vol. 365 (1993), pp. 715 721.
CHAPTER 7, AMONG THE MOONS OF SATURN
Jonathan Lunine, "Does Titan Have Oceans?," American Scientist, vol. 82 (1994), pp. 134 144.
Carl Sagan, W. Reid Thompson, and Bishun N. Khare, "Titan: A Laboratory for Prebiological Organic
Chemistry," Accounts of Chemical Research, vol. 25 (1992), pp. 286 292.
J. William Schopf, Major Events in the History of Life (Boston: Jones and Bartlett, 1992).
CHAPTER 8, THE FIRST NEW PLANET
Bernard Cohen, "G. D. Cassini and the Number of the Planets," in Nature, Experiment and the Sciences,
Trevor Levere and W. R. Shea, editors (Dordrecht: Kluwer, 1990).
CHAPTER 9, AN AMERICAN SHIP AT THE FRONTIERS OF THE SOLAR SYSTEM
Murmurs of Earth, CD ROM of the Voyager interstellar record, with introduction by Carl Sagan and
Ann Druyan (Los Angeles: Warner New Media, 1992), WNM 14022.
Alexander Wolszczan, "Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR
B1257+12," Science, vol. 264 (1994), pp. 538 542.
CHAPTER 12, THE GROUND MELTS
Peter Cattermole, Venus: The Geological Survey (Baltimore: Johns Hopkins University Press, 1994).
Peter Francis, Volcanoes: A Planetary Perspective (Oxford: Oxford University Press, 1993).
CHAPTER 13, THE GIFT OF APOLLO
Andrew Chaikin, A Man on the Moon (New York: Viking, 1994).
Michael Collins, Liftoff (New York: Grove Press, 1988).
Daniel Deudney, "Forging Missiles into Spaceships," World Policy Journal, vol. 2, no. 2 (Spring 1985), pp. 271 303.
Harry Hurt, For All Mankind (New York: Atlantic Monthly Press, 1988).
Richard S. Lewis, The Voyages of Apollo: The Exploration of the Moon (New York: Quadrangle, 1974).
Walter A. McDougall, The Heavens and the Earth: A Political History of the Space Age (New York:
Basic Books, 1985).
Alan Shepherd, Deke Slayton et al., Moonshot (Atlanta: Hyperion, 1994).
Don E. Wilhelms, To a Rocky Moon: A Geologist's History or Lunar Exploration (Tucson: University of
Arizona Press, 1993).
CHAPTER 14, EXPLORING OTHER WORLDS AND PROTECTING THIS ONE
Kevin W. Kelley, editor, The Home Planet (Reading, MA: AddisonWesley, 1988).
Carl Sagan and Richard Turco, A Path Where No Man Thought: Nuclear Winter and the End of the Arms
Race (New York: Random House, 1990).
Richard Turco, Earth Under Siege: Air Pollution and Global Change (New York: Oxford University
Press, in press).
CHAPTER 15, THE GATES OF THE WONDER WORLD OPEN
Victor R. Baker, The Channels of Mars (Austin: University of Texas Press, 1982).
Michael H. Carr, The Surface of Mars (New Haven: Yale University Press, 1981).
H. H. Kieffer, B. M. Jakosky, C. W. Snyder, and M. S. Matthews, editors, Mars (Tucson: University of Arizona
Press, 1992).
John Noble Wilford, Mars Beckons: The Mysteries, the Challenges, the Expectations of Our Next Great
Adventure in Space (New York: Knopf, 1990).
CHAPTER 18, THE MARSH OF CAMARINA
Clark R. Chapman and David Morrison, "Impacts on the Earth by Asteroids and Comets: Assessing the Hazard,"
Nature, vol. 367 (1994), pp. 3340.
A. W. Harris, G. Canavan, C. Sagan, and S. J. Ostro, "The Deflection Dilemma: Use vs. Misuse of Technologies
for Avoiding Interplanetary Collision Hazards," in Hazards Due to Asteroids and Comets, T. Gehrels,
editor (Tucson: University of Arizona Press, 1994).
John S. Lewis and Ruth A. Lewis, Space Resources: Breaking the Bonds of Earth (New York: Columbia
University Press, 1987).
C. Sagan and S. J. Ostro, "Long Range Consequences of Interplanetary Collision Hazards," Issues in Science and
Technology (Summer 1994), pp. 67 72.
CHAPTER 19, REMAKING THE PLANETS
J. D. Bernal, The World, the Flesh, and the Devil (Bloomington, IN: Indiana University Press, 1969; first edition,
1929).
James B. Pollack and Carl Sagan, "Planetary Engineering," in J. Lewis and M. Matthews, editors, Near Earth
Resources (Tucso
n: University of Arizona Press, 1992).
CHAPTER 20, DARKNESS
Frank Drake and Dava Sobel, Is Anyone Out There? (New York: Delacorte, 1992).
Paul Horowitz and Carl Sagan, "Project META: A Five Year All Sky Narrowband Radio Search for
Extraterrestrial Intelligence," Astrophysical Journal, vol. 415 (1992), pp. 218 235.
Thomas R. McDonough, The Search for Extraterrestrial Intelligence (New York: John Wiley and Sons, 1987).
Carl Sagan, Contact: A Novel (New York: Simon and Schuster, 1985) .
CHAPTER 21, TO THE SKY!
J. Richard Gott III, "Implications of the Copernican Principle for Our Future Prospects," Nature, vol. 263 (1993),
pp. 315 319.
CHAPTER 22, TIPTOEING THROUGH THE MILKY WAY
I. A. Crawford, "Interstellar Travel: A Review for Astronomers," Quarterly Journal of the Royal Astronomical
Society, vol. 31 (1990), p. 377.
I. A. Crawford, "Space, World Government, and `The End of History,' "Journal of the British Interplanetary
Society, vol. 46 (1993), pp. 415 420.
Freeman J. Dyson, The World, the Flesh, and the Devil (London: Birkbeck College, 1972).
Ben R. Finney and Eric M. Jones, editors, Interstellar Migration and the Human Experience (Berkeley:
University of California Press, 1985).
Francis Fukuyama, The End of History and the Last Man (New York: The Free Press, 1992).
Charles Lindholm, Charisma (Oxford: Blackwell, 1990). The comment on the need for a telos is in this book.