by Carl Sagan
Copyright © 1978 by Carl Sagan
All rights reserved under International and Pan-American Copyright Conventions. Published in the United States by Ballantine Books, a division of Random House, Inc., New York and simultaneously in Canada by Random House of Canada, Limited, Toronto, Canada.
Library of Congress Cataloging in Publication Data
Main entry under title:
Murmurs of earth.
Reprint of the ed. published by Random House, New York.
Includes index.
CONTENTS: Sagan, C. For future times and beings.—Drake, F. D. The foundations of the Voyager record.—Lomberg, J. Pictures of earth.—Sagan, L. S. A Voyager’s greetings.—Druyan, A. The sounds of earth.—Ferris, T. Voyager’s music.—Sagan, C. The Voyager mission to the outer solar system.—Sagan, C. Epilogue.
1. Project Voyager—Addresses, essays, lectures. I. Sagan, Carl, 1934-
[TL789.8.U6V685 1979] 001.55′0999 79-15209
eBook ISBN: 978-0-307-80202-6
Trade Paperback ISBN: 978-0-679-74444-3
This edition published in hardcover by Random House, Inc.
First Ballantine Books Edition: November 1979
v3.1
To the makers of music—all worlds, all times
The Contents of the Voyager Record
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118 pictures
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The first two bars of the Beethoven Cavatina
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Greetings from the President of the United States
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Congressional List
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Greetings from the Secretary General of the United Nations
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Greetings in fifty-four languages
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UN Greetings
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Whale Greetings
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The Sounds of Earth
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Music
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Contents
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Cover
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Title Page
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Copyright
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Dedication
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Preface
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1 For Future Times and Beings, by Carl Sagan
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2 The Foundations of the Voyager Record, by F. D. Drake
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3 Pictures of Earth, by Jon Lomberg
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4 A Voyager’s Greetings, by Linda Salzman Sagan
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5 The Sounds of Earth, by Ann Druyan
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6 Voyager’s Music, by Timothy Ferris
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7 The Voyager Mission to the Outer Solar System, by Carl Sagan
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Epilogue, by Carl Sagan
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Acknowledgments
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Appendices
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Index
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About the Authors
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On August 20th and September 5th, 1977, two extraordinary spacecraft called Voyager were launched to the stars. After what promises to be a detailed and thoroughly dramatic exploration of the outer solar system from Jupiter to Uranus between 1979 and 1986, these space vehicles will slowly leave the solar systems—emissaries of Earth to the realm of the stars. Affixed to each Voyager craft is a gold-coated copper phonograph record as a message to possible extraterrestrial civilizations that might encounter the spacecraft in some distant space and time. Each record contains 118 photographs of our planet, ourselves and our civilization; almost 90 minutes of the world’s greatest music; an evolutionary audio essay on “The Sounds of Earth”; and greetings in almost sixty human languages (and one whale language), including salutations from the President of the United States and the Secretary General of the United Nations. This book is an account, written by those chiefly responsible for the contents of the Voyager Record, of why we did it, how we selected the repertoire, and precisely what the record contains.
Carl Sagan
F. D. Drake
Ann Druyan
Timothy Ferris
Jon Lomberg
Linda Salzman Sagan
February 1978
“I had monuments made of bronze, lapis lazuli, alabaster … and white limestone … and inscriptions of baked clay … I deposited them in the foundations and left them for future times,”
—Esarhaddon, king of Assyria, seventh century B.C.
The Trylon (right) and Perisphere (center) of the 1939 New York World’s Fair. The statuary at left represents Four Victories of Peace, by John Gregory.
In 1939, before my fifth birthday, my parents took me to the New York World’s Fair. It exhibited wonders. Lightning was made to crackle, blue and fearsome, between two metal spheres. A sign read “Hear light! See sound!” and it turned out that, sure enough, such things were possible. There were buildings devoted to strange cultures and faraway lands of whose very existence I had been totally ignorant. The centerpiece of that World’s Fair was the Trylon and Perisphere, a stately, tapering tower and a building-sized sphere in which was something called “The World of Tomorrow.” You walked on a high-railed ramp and below you, in miniature, was an exquisitely detailed model of the future—graceful aerial skyways filled with streamlined automobiles and happy citizens purposefully intent on some futuristic business, the nature of which was difficult to divine from the perspective of my limited experience and abbreviated stature. But one message was clearly communicated: there were other cultures and there would be future times.
The confidence in the future evinced by that World’s Fair was dramatically illustrated by the Time Capsule, a chamber “hermetically sealed,” filled with newspapers, books and artifacts of 1939, buried in Flushing Meadows to be opened and revealed automatically in some distant epoch. Why? Because the future would be different from the present. Because those in the future would want to know about our time, as we are curious about our antecedents’. Because there was something graceful and very human in the gesture, hands across the centuries, an embrace of our descendants and our posterity.
There have been many time capsules both before and since. Esarhaddon, son of Sennacherib, was a mighty general and an able administrator, but he also had a conscious interest in presenting not just his military glory but his entire civilization to the future, burying cuneiform inscriptions in the foundation stones of monuments and other buildings. Esarhaddon was king of Assyria, Babylonia and Egypt. His military campaigns extended from the mountains of Armenia to the deserts of Arabia. For all that, his name is hardly a household word today, but his works have made a significant contribution to our knowledge of the Middle East in the seventh century B.C. His son and successor, Assurbanipal, perhaps influenced by the time-capsule tradition of his father, accumulated a massive library on stone tablets comprising the knowledge of all that was known in that remote epoch. The remains of Assurbanipal’s library are a remarkable resource for scholars of today. Esarhaddon and Assurbanipal have spoken clearly down through the centuries and millennia. For those who have done something they consider worthwhile, communication to the future is an almost irresistible temptation, and it has been attempted in virtually every human culture. In the best of cases, it is an optimistic and far-seeing act; it expresses great hope about the future; it time-binds the human community; it gives us a perspective on the significance of our own actions at this moment in the long historical journey of our species.
The coming of the space age has brought with it an interest in communication over time intervals far longer than any Esarhaddon could have imagined, as well as the means to send messages to the distant futur
e. We have gradually realized that we humans are only a few million years old on a planet a thousand times older. Our modern technical civilization is one ten-thousandth as old as mankind. What we know well has lasted no longer than the blink of an eyelash in the enterprise of cosmic time. Our epoch is not the first or the best. Events are occurring at a breathless pace and no one knows what tomorrow will bring—whether our present civilization will survive the perils that face us and be transformed, or whether in the next century or two we will destroy our technological society. But in either case it will not be the end of the human species.
There will be other people and other civilizations, and they will be different from us. Our civilization is the product of a particular path our ancestors have followed among the vagaries of historical alternatives. Had events of the distant past taken a slightly different turn, our surroundings and thought processes, what we find natural and hold dear, might be very different. Despite our everyday sense that things should of course be the way they are, the details of our particular civilization are extraordinarily unlikely, and it is easy to imagine a set of historical events which would have led to a rather different civilization—for example, one in which Constantine was converted to Mithraism after the Battle of the Milvian Bridge, in which a subsequent intellectual revolt against institutionalized Mithraism led to a Persian-based Renaissance, in which bulls and scorpions were still dominant cultural motifs. Citizens of such a civilization would consider it to be perfectly ordinary and reasonable and a civilization like ours the merest historical romancing. This lack of historical determinism in the details of a civilization means that those details are of extraordinary value, not just to professional historians but to all who wish to understand the nature of culture. I think it is this respect for the integuments of a civilization that, above all other reasons, makes us sympathetic to the enterprise of time capsuling.
But Earth is only one small planet among nine or so that endlessly circle our star, the Sun; and the Sun is but one of some 250 billion stars that make up a great whirling pinwheel of gas and dust and stars called the Milky Way galaxy. In turn, the Milky Way is one of perhaps hundreds of billions of other galaxies. While we are still profoundly ignorant about many of the details, there is evidence that planets are a common accompaniment of stars and that the chemical steps that led to the origin of life on Earth some four billion years ago require only the most common cosmic conditions.
Many scientists therefore now think it likely—although it is by no means guaranteed—that innumerable other planets have seen the origin of simple forms of life, their slow evolution into more complex forms, the development of beings with some degree of intelligence and ability to manipulate the environment, and eventually the emergence of a technological civilization. The creatures on such other planets would be astonishingly different from human beings or any other creatures that inhabit our little planetary home, the Earth. Like history, evolution proceeds in a multitude of small and unpredictable steps, the variation in any one of which producing profound differences later on. Beings elsewhere might think as well as we do or better; they might be better poets or engineers or philosophers: they might have superior moral or aesthetic standards; but they will not be human beings or anything even close. Likewise, the details and integuments of their civilizations, constructed by beings profoundly different to begin with, on an alien planet with a different environment and different life styles required for survival, should be far stranger than any proposition posed in space fantasy or science fiction.
And yet there is an argument—perhaps it is only a hope—that we might be able to communicate with representatives of such exotic civilizations, because they, like we, must come to grips with the same laws of physics and chemistry and astronomy. The composition of a star and its spectral properties are not fundamentally impositions that scientists have made on nature, but rather the other way around. There is an external reality that we ignore at our peril, and indeed much of the evolution of the human species can be described as an increasing concordance between the images within our brains and the reality in the external world. Thus, whatever the differences in starting points, there must come to be a gradual convergence in intellectual content and discipline between diverse planetary species.
So if it is possible to communicate, we think we know what the first communications will be about: They will be about the one thing the two civilizations are guaranteed to share in common, and that is science. The greatest interest might be in communicating information on music, say, or social conventions; but the first successful communications will in fact be scientific.
And how might such communication be effected? Space vehicles travel very slowly. A typical mission to the Moon lasts a few days, to the nearby planets a few months, to the outer solar system a few years. We do not expect other civilizations among the planets in the Sun’s family. Even quite optimistic estimates place the nearest civilization at a few hundred light-years, where a light-year is almost six trillion miles. It would take our present spacecraft some tens of thousands of years to go the distance of the nearest star, and several tens of millions of years to travel this estimated distance to the nearest other civilization.
A much quicker and more reliable means of interstellar communication is to send or receive radio messages that travel at the speed of light. Our present radio technology is fully adequate for this purpose and several attempts have been made to listen to a few hundred nearby stars and galaxies for possible intelligent signals, but so far without positive results. There are so many stars and we have so little information about which are the likely candidates that it would be astonishing if the very first efforts were rewarded with success. A long-term effort of a few dedicated radio telescopes for at least some decades is required. Only one attempt has been made by radio astronomers to send a message into space. This occurred in November 1974 at the dedication of the resurfacing of the great Arecibo radio telescope in Puerto Rico, and was not so much a serious effort at interstellar communication as a demonstration of the great powers that radio technology has put at our command. It is described further in Frank Drake’s chapter, “The Foundations of the Voyager Record,” below.
There is a major difference between sending and receiving. We have only recently achieved the capability of doing either, and any civilization even a little bit behind us technologically could do neither. Therefore, a baby civilization like ours is not a civilization that might be expected to transmit; the technology of any other communicative civilization should be far in advance of our own. In addition, the immense distances between the stars means that it would be a very long time—probably many hundreds of years—before any signal we transmit could be answered by a civilization on a planet of some other star. As a practical means of instituting interstellar dialogue, neither radio signals nor interstellar spacecraft is appropriate, and we must instead concentrate on the receipt of monologues from elsewhere. The primary approach quite properly is the search for radio messages transmitted in our direction by more advanced civilizations.
But it is hard to resist sending out something ourselves. Most interplanetary spacecraft will pass by the target planet and remain in a long, looping trajectory around the Sun, to become artificial planets of the solar system. Others will orbit or land on the target planet. But occasionally a kind of game of interplanetary billiards occurs, in which the gravity of one planet is used to assist the spacecraft in a short-time fast trajectory to another, more distant, world. The first such missions, by the Pioneer 10 and 11 spacecraft, were launched in 1971 and in 1972 to examine Jupiter. The Jupiter swing-by accelerated Pioneer 11 so that it flies by Saturn in 1979. But the close passage by Jupiter for both Pioneers 10 and 11 results in an extraordinary flight path: they are now irretrievably set on trajectories that will take them out of the solar system. Pioneers 10 and 11 are mankind’s first interstellar probes. The characteristic speeds of such spacecraft are about ten kilometers per second with respect to the Earth
. They therefore travel about one astronomical unit, the distance between Earth and the Sun, every six months. They take two and a half years to go to Jupiter, five to Saturn, fifteen to Neptune, twenty to Pluto, and more than ten thousand years to the belt of dead cometary husks that slowly orbit the Sun in the dark of the outer solar system. It is only then that they enter the realm of the stars.
The radio transmitters of Pioneers 10 and 11 will be dead long before they reach even the orbit of Pluto, much less the distance to the nearest star. They are condemned to wander passively and forever in the depths of interstellar space. Or at least probably forever. The chance of Pioneers 10 and 11 entering another planetary system in, say, the next 10 billion years, is tiny, even if every star in the Milky Way galaxy has planets. The reason is that the distances between the stars are very great, and space is very empty. It is a little like randomly throwing a dart in the dark in Madison Square Garden, to whose walls are affixed twenty balloons. There is some chance of puncturing a balloon, but the likelihood of success is stupefyingly small.
Nevertheless, Pioneers 10 and 11 are our first interstellar space vehicles, and they contain a message. Affixed to one of the antenna support struts of each spacecraft is a six- by nine-inch gold-anodized aluminum plaque on which is etched a drawing that describes something of the epoch and locale of our civilization, portrayed in a scientific language we hope is comprehensible to a scientifically literate society with no prior knowledge of our planet or its inhabitants. The plaque also contains a sketch of two representatives of the human species greeting the cosmos with hope. Three of the authors of this book were responsible for the design of the Pioneer 10 and 11 plaques, and more details about it can be found in the next chapter.