by Carl Sagan
A very different kind of contact is much more likely—the case we have already discussed in which we receive a rich, complex message, probably by radio, from another civilization in space, but do not make, at least for a while, physical contact with them. In this case there is no way for the transmitting civilization to know whether we have received the message. If we find the contents offensive or frightening, we are not obliged to reply. But if the message contains valuable information, the consequences for our own civilization will be stunning—insights on alien science and technology, art, music, politics, ethics, philosophy and religion, and most of all, a profound deprovincialization of the human condition. We will know what else is possible.
Because we will share scientific and mathematical insights with any other civilization, I believe that understanding the interstellar message will be the easiest part of the problem. Convincing the U.S. Congress and the Council of Ministers of the U.S.S.R. to fund a search for extraterrestrial intelligence is the hard part.* In fact, it may be that civilizations can be divided into two great categories: one in which the scientists are unable to convince nonscientists to authorize a search for extraplanetary intelligence, in which energies are directed exclusively inward, in which conventional perceptions remain unchallenged and society falters and retreats from the stars; and another category in which the grand vision of contact with other civilizations is shared widely, and a major search is undertaken.
This is one of the few human endeavors where even a failure is a success. If we were to carry out a rigorous search for extraterrestrial radio signals encompassing millions of stars and heard nothing, we would conclude that galactic civilizations were at best extremely rare, a calibration of our place in the universe. It would speak eloquently of how rare are the living things of our planet, and would underscore, as nothing else in human history has, the individual worth of every human being. If we were to succeed, the history of our species and our planet would be changed forever.
It would be easy for extraterrestrials to make an unambiguously artificial interstellar message. For example, the first ten prime numbers—numbers divisible only by themselves and by one—are 1, 2, 3, 5, 7, 11, 13, 17, 19, 23. It is extremely unlikely that any natural physical process could transmit radio messages containing prime numbers only. If we received such a message we would deduce a civilization out there that was at least fond of prime numbers. But the most likely case is that interstellar communication will be a kind of palimpsest, like the palimpsests of ancient writers short of papyrus or stone who superimposed their messages on top of preexisting messages. Perhaps at an adjacent frequency or a faster timing, there would be another message, which would turn out to be a primer, an introduction to the language of interstellar discourse. The primer would be repeated again and again because the transmitting civilization would have no way to know when we tuned in on the message. And then, deeper in the palimpsest, underneath the announcement signal and the primer, would be the real message. Radio technology permits that message to be inconceivably rich. Perhaps when we tuned in, we would find ourselves in the midst of Volume 3,267 of the Encyclopaedia Galactica.
We would discover the nature of other civilizations. There would be many of them, each composed of organisms astonishingly different from anything on this planet. They would view the universe somewhat differently. They would have different arts and social functions. They would be interested in things we never thought of. By comparing our knowledge with theirs, we would grow immeasurably. And with our newly acquired information sorted into a computer memory, we would be able to see which sort of civilization lived where in the Galaxy. Imagine a huge galactic computer, a repository, more or less up-to-date, of information on the nature and activities of all the civilizations in the Milky Way Galaxy, a great library of life in the Cosmos. Perhaps among the contents of the Encyclopaedia Galactica will be a set of summaries of such civilizations, the information enigmatic, tantalizing, evocative—even after we succeed in translating it.
Eventually, taking as much time as we wished, we would decide to reply. We would transmit some information about ourselves—just the basics at first—as the start of a long interstellar dialogue which we would begin but which, because of the vast distances of interstellar space and the finite velocity of light, would be continued by our remote descendants. And someday, on a planet of some far distant star, a being very different from any of us would request a printout from the latest edition of the Encyclopaedia Galactica and acquire a little information about the newest society to join the community of galactic civilizations.
Civilization Type: 1.8 L.
Society Code: 2A11,
“We Who Survived”.
Star: F0, spectrum variable,
r=9.717 kpc, θ = 0°07’51″,
Φ = 210°20’37″.
Planet: sixth, a=2.4 × 1013 cm,
M = 7 × 1018 g, R=2.1 × 109cm,
p = 2.7 × 106s, P = 4.5 × 107s.
Extraplanetary colonies: none.
Planet age: 1.14 × 1017 s.
First locally initiated contact: 2.6040 × 108 s ago.
Receipt first galactic nested code: 2.6040 × 108 s ago.
Biology: C,N,0,H,S,Se,Cl,Br,
H2O, S8, polyaromatic sulfonyl
halides. Mobile
photochemosynthetic
autotrophs in weakly reducing
atmosphere.
Polytaxic, monochromatic.
m≈3 × 1012g, t≈5 × 1010 s.
No genetic prosthesis.
Genomes: ~6 × 107
(nonredundant
bits/genome: ~2 × 1012).
Technology: exponentiating,
approaching asymptotic limit.
Culture: global, nongregarious,
polyspecific (2 genera,
41 species); arithmetic
poetry.
Prepartum/postpartum:
0.52 [30],
Individual/communal:
0.73 [14],
Artistic/technological:
0.81 [18].
Probability of survival
(per 100 yr): 80%.
Civilization Type: 2.3 R.
Society Code: 1H1,
“We Who Became One”.
Interstellar civilization, no
planetary communities,
utilizes 1504 supergiants,
0, B, A stars and pulsars.
Civilization Age: 6.09 × 1015 s.
First locally initiated contact:
6.09 ×1015 s ago.
Receipt first galactic nested
code: 6.09 × 1015 s ago.
Source civilization, neutrino
channel.
Local Group polylogue.
Biology: C,H,O,Be,Fe,Ge,He.
4K metal-chelated organic
semiconductors, types
various.
Cryogenic superconducting
electrovores with neutron
crystal dense packing and
modular starminers; polytaxic.
m various, t≈5 × 1015 s.
Genomes: 6 × 1017
(nonredundant bits/mean
genome: ~3 × 1017).
Probability of survival
(per 106 yr):99%.
Hypothetical computer summaries of two advanced civilizations from the Encyclopaedia Galactica. By Jon Lomberg and the author.
Civilization Type: 1.0 J.
Society Code: 4G4, “Humanity”.
Star: G2, r=9.844 kpc, θ = 00°05’24″,θ = 206°28’49″.
Planet: third, a=1.5 × 1013 cm, M = 6 × 1027 g, = 6.4 × 108 cm, p = 8.6 × 104 s, P = 3.2 × 107 s.
Extraplanetary colonies: none.
Planet age: 1.45 × 1017 s.
First locally initiated contact: 1.21 × 109 s ago.
Receipt first galactic nested code: application pending.
Biology: C,N,O,S,H2O,PO4.
Deoxyribonucleic acid.
No genetic prosthesis.
Mobile
heterotrophs, symbionts
with photosynthetic
autotrophs. Surface dwellers,
monospecific, polychromatic
O2 breathers. Fe-chelated
tetrapyroles in circulatory
fluid. Sexual mammals.
m≈7 × 104, t≈2 × 109s.
Genomes: 4 × 109.
Technology: exponentiating/
fossil fuels/nuclear weapons/
organized warfare/
environmental pollution.
Culture: ~200 nation states,
~6 global powers; cultural
and technological
homogeneity underway.
Prepartum/postpartum:
0.21 [18],
Individual/communal:
0.31 [17],
Artistic/technological:
0.14 [11].
Probability of survival
(per 100 yr): 40%.
Hypothetical summary of a newly emerged technical civilization from the Encyclopaedia Galactica. By Jon Lomberg and the author.
*Fourier is now famous for his study of the propagation of heat in solids, used today to understand the surface properties of the planets, and for his investigation of waves and other periodic motion—a branch of mathematics known as Fourier analysis.
*When La Pérouse was mustering the ship’s company in France, there were many bright and eager young men who applied but were turned down. One of them was a Corsican artillery officer named Napoleon Bonaparte. It was an interesting branch point in the history of the world. If La Pérouse had accepted Bonaparte, the Rosetta stone might never have been found. Champollion might never have decrypted Egyptian hieroglyphics, and in many more important respects our recent history might have been changed significantly.
*The account of Cowee, the Tlingit chief, shows that even in a preliterate culture a recognizable account of contact with an advanced civilization can be preserved for generations. If the Earth had been visited hundreds of thousands of years ago by an advanced extraterrestrial civilization, even if the contacted culture was preliterate, we might well expect to have some recognizable form of the encounter preserved. But there is not a single case in which a legend reliably dated from earlier pretechnological times can be understood only in terms of contact with an extraterrestrial civilization.
*There may be many motivations to go to the stars. If our Sun or a nearby star were about to go supernova, a major program of interstellar spaceflight might suddenly become attractive. If we were very advanced, the discovery that the galactic core was imminently to explode might even generate serious interest in transgalactic or intergalactic spaceflight. Such cosmic violence occurs sufficiently often that nomadic spacefaring civilizations may not be uncommon. Even so, their arrival here remains unlikely.
*Or other national organs. Consider this pronouncement from a British Defence Department spokesman as reported in the London Observer for February 26, 1978: “Any messages transmitted from outer space are the responsibility of the BBC and the Post Office. It is their responsibility to track down illegal broadcasts.”
CHAPTER XIII
WHO SPEAKS FOR EARTH?
To what purpose should I trouble myself in searching out the secrets of the stars, having death or slavery continually before my eyes?
—A question put to Pythagoras by Anaximenes (c. 600 B.C.),
according to Montaigne
How vast those Orbs must be, and how inconsiderable this Earth, the Theatre upon which all our mighty Designs, all our Navigations, and all our Wars are transacted, is when compared to them. A very fit consideration, and matter of Reflection, for those Kings and Princes who sacrifice the Lives of so many People, only to flatter their Ambition in being Masters of some pitiful corner of this small Spot.
—Christiaan Huygens, New Conjectures Concerning the Planetary
Worlds, Their Inhabitants and Productions, c. 1690
We look back through countless millions of years and see the great will to live struggling out of the intertidal slime, struggling from shape to shape and from power to power, crawling and then walking confidently upon the land, struggling generation after generation to master the air, creeping down into the darkness of the deep; we see it turn upon itself in rage and hunger and reshape itself anew, we watch it draw nearer and more akin to us, expanding, elaborating itself, pursuing its relentless inconceivable purpose, until at last it reaches us and its being beats through our brains and arteries … It is possible to believe that all the past is but the beginning of a beginning, and that all that is and has been is but the twilight of the dawn. It is possible to believe that all that the human mind has ever accomplished is but the dream before the awakening … Out of our … lineage, minds will spring, that will reach back to us in our littleness to know us better than we know ourselves. A day will come, one day in the unending succession of days, when beings, beings who are now latent in our thoughts and hidden in our loins, shall stand upon this earth as one stands upon a footstool, and shall laugh and reach out their hands amidst the stars.
—H. G. Wells, “The Discovery of the Future,” Nature 65, 326
(1902)
The Cosmos was discovered only yesterday. For a million years it was clear to everyone that there were no other places than the Earth. Then in the last tenth of a percent of the lifetime of our species, in the instant between Aristarchus and ourselves, we reluctantly noticed that we were not the center and purpose of the Universe, but rather lived on a tiny and fragile world lost in immensity and eternity, drifting in a great cosmic ocean dotted here and there with a hundred billion galaxies and a billion trillion stars. We have bravely tested the waters and have found the ocean to our liking, resonant with our nature. Something in us recognizes the Cosmos as home. We are made of stellar ash. Our origin and evolution have been tied to distant cosmic events. The exploration of the Cosmos is a voyage of self-discovery.
As the ancient mythmakers knew, we are the children equally of the sky and the Earth. In our tenure on this planet we have accumulated dangerous evolutionary baggage, hereditary propensities for aggression and ritual, submission to leaders and hostility to outsiders, which place our survival in some question. But we have also acquired compassion for others, love for our children and our children’s children, a desire to learn from history, and a great soaring passionate intelligence—the clear tools for our continued survival and prosperity. Which aspects of our nature will prevail is uncertain, particularly when our vision and understanding and prospects are bound exclusively to the Earth—or, worse, to one small part of it. But up there in the immensity of the Cosmos, an inescapable perspective awaits us. There are not yet any obvious signs of extraterrestrial intelligence and this makes us wonder whether civilizations like ours always rush implacably, headlong, toward self-destruction. National boundaries are not evident when we view the Earth from space. Fanatical ethnic or religious or national chauvinisms are a little difficult to maintain when we see our planet as a fragile blue crescent fading to become an inconspicuous point of light against the bastion and citadel of the stars. Travel is broadening.
There are worlds on which life has never arisen. There are worlds that have been charred and ruined by cosmic catastrophes. We are fortunate: we are alive; we are powerful; the welfare of our civilization and our species is in our hands. If we do not speak for Earth, who will? If we are not committed to our own survival, who will be?
The human species is now undertaking a great venture that if successful will be as important as the colonization of the land or the descent from the trees. We are haltingly, tentatively breaking the shackles of Earth—metaphorically, in confronting and taming the admonitions of those more primitive brains within us; physically, in voyaging to the planets and listening for the messages from the stars. These two enterprises are linked indissolubly. Each, I believe, is a necessary condition for the other. But our energies are directed far more toward war. Hypnotized by mutual mistrust, almost never concerned for the species
or the planet, the nations prepare for death. And because what we are doing is so horrifying, we tend not to think of it much. But what we do not consider we are unlikely to put right.
Every thinking person fears nuclear war, and every technological state plans for it. Everyone knows it is madness, and every nation has an excuse. There is a dreary chain of causality: The Germans were working on the bomb at the beginning of World War II; so the Americans had to make one first. If the Americans had one, the Soviets had to have one, and then the British, the French, the Chinese, the Indians, the Pakistanis … By the end of the twentieth century many nations had collected nuclear weapons. They were easy to devise. Fissionable material could be stolen from nuclear reactors. Nuclear weapons became almost a home handicraft industry.
The conventional bombs of World War II were called blockbusters. Filled with twenty tons of TNT, they could destroy a city block. All the bombs dropped on all the cities in World War II amounted to some two million tons, two megatons, of TNT—Coventry and Rotterdam, Dresden and Tokyo, all the death that rained from the skies between 1939 and 1945: a hundred thousand blockbusters, two megatons. By the late twentieth century, two megatons was the energy released in the explosion of a single more or less humdrum thermonuclear bomb: one bomb with the destructive force of the Second World War. But there are tens of thousands of nuclear weapons. By the ninth decade of the twentieth century the strategic missile and bomber forces of the Soviet Union and the United States were aiming warheads at over 15,000 designated targets. No place on the planet was safe. The energy contained in these weapons, genies of death patiently awaiting the rubbing of the lamps, was far more than 10,000 megatons—but with the destruction concentrated efficiently, not over six years but over a few hours, a blockbuster for every family on the planet, a World War II every second for the length of a lazy afternoon.