Cosmos (48 page)
Authors: Carl Sagan
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 × 10
13
cm,
M = 7 × 10
18
g, R=2.1 × 10
9
cm,
p = 2.7 × 10
6
s, P = 4.5 × 10
7
s.
Extraplanetary colonies: none.
Planet age: 1.14 × 10
17
s.
First locally initiated contact: 2.6040 × 10
8
s ago.
Receipt first galactic nested code: 2.6040 × 10
8
s ago.
Biology: C,N,0,H,S,Se,Cl,Br,
H
2
O, S
8
, polyaromatic sulfonyl
halides. Mobile
photochemosynthetic
autotrophs in weakly reducing
atmosphere.
Polytaxic, monochromatic.
m≈3 × 10
12
g, t≈5 × 10
10
s.
No genetic prosthesis.
Genomes: ~6 × 10
7
(nonredundant
bits/genome: ~2 × 10
12
).
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, Astars and pulsars.
Civilization Age: 6.09 × 10
15
s.
First locally initiated contact:
6.09 ×10
15
s ago.
Receipt first galactic nested
code: 6.09 × 10
15
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 × 10
15
s.
Genomes: 6 × 10
17
(nonredundant bits/mean
genome: ~3 × 10
17
).
Probability of survival
(per 10
6
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 × 10
13
cm, M = 6 × 10
27
g, = 6.4 × 10
8
cm, p = 8.6 × 10
4
s, P = 3.2 × 10
7
s.
Extraplanetary colonies: none.
Planet age: 1.45 × 10
17
s.
First locally initiated contact: 1.21 × 10
9
s ago.
Receipt first galactic nested code: application pending.
Biology: C,N,O,S,H
2
O,PO
4
.
Deoxyribonucleic acid.
No genetic prosthesis.
Mobile heterotrophs, symbionts
with photosynthetic
autotrophs. Surface dwellers,
monospecific, polychromatic
O
2
breathers. Fe-chelated
tetrapyroles in circulatory
fluid. Sexual mammals.
m≈7 × 10
4
, t≈2 × 10
9
s.
Genomes: 4 × 10
9
.
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.”
