Cosmos - Carl Sagan [161]
But consider the alternative, the prospect that at least some civilizations learn to live with high technology; that the contradictions posed by the vagaries of past brain evolution are consciously resolved and do not lead to self-destruction; or that, even if major disturbances do occur, they are reversed in the subsequent billions of years of biological evolution. Such societies might live to a prosperous old age, their lifetimes measured perhaps on geological or stellar evolutionary time scales. If 1 percent of civilizations can survive technological adolescence, take the proper fork at this critical historical branch point and achieve maturity, then fL ≈ 1/100, N ≈ 107, and the number of extant civilizations in the Galaxy is in the millions. Thus, for all our concern about the possible unreliability of our estimates of the early factors in the Drake equation, which involve astronomy, organic chemistry and evolutionary biology, the principal uncertainty comes down to economics and politics and what, on Earth, we call human nature. It seems fairly clear that if self-destruction is not the overwhelmingly preponderant fate of galactic civilizations, then the sky is softly humming with messages from the stars.
These estimates are stirring. They suggest that the receipt of a message from space is, even before we decode it, a profoundly hopeful sign. It means that someone has learned to live with high technology; that it is possible to survive technological adolescence. This alone, quite apart from the contents of the message, provides a powerful justification for the search for other civilizations.
If there are millions of civilizations distributed more or less randomly through the Galaxy, the distance to the nearest is about two hundred light-years. Even at the speed of light it would take two centuries for a radio message to get from there to here. If we had initiated the dialogue, it would be as if the question had been asked by Johannes Kepler and the answer received by us. Especially because we, new to radio astronomy, must be comparatively backward, and the transmitting civilization advanced, it makes more sense for us to listen than to send. For a more advanced civilization, the positions are, of course, reversed.
We are at the earliest stages of our radio search for other civilizations in space. In an optical photograph of a dense star field, there are hundreds of thousands of stars. By our more optimistic estimates, one of them is the site of an advanced civilization. But which one? Toward which stars should we point our radio telescopes? Of the millions of stars that may mark the location of advanced civilizations, we have so far examined by radio no more than thousands. We have made about one-tenth of one percent of the required effort. But a serious, rigorous, systematic search will come soon. The preparatory steps are now underway, both in the United States and in the Soviet Union. It is comparatively inexpensive: the cost of a single naval vessel of intermediate size—a modern destroyer, say—would pay for a decade-long program in the search for extraterrestrial intelligence.
Benevolent encounters have not been the rule in human history, where transcultural contacts have been direct and physical, quite different from the receipt of a radio signal, a contact as light as a kiss. Still, it is instructive to examine one or two cases from our past, if only to calibrate our expectations: Between the times of the American and the French Revolutions, Louis XVI of France outfitted an expedition to the Pacific Ocean, a voyage with scientific, geographic, economic and nationalistic objectives. The commander was the Count of La Pérouse, a noted explorer who had fought for the United States in its War of Independence. In July 1786, almost a year after setting sail, he reached the coast of Alaska, a place now called Lituya Bay. He was delighted with the harbor and wrote: “Not a port in the universe could afford more conveniences.” In this exemplary location, La Pérouse
perceived some savages, who made signs of friendship,