Page Content (OCR)
118 Five SETI scientists, writing in 1977, thought that within a few decades mankind will either have discovered the presence of extraterrestrial intel- ligence or will have placed very severe constraints on the likelihood that such intelligence exists. Shostak addressed the same time frame in a more upbeat way: “If the galaxy is populated by only ten thousand advanced civilizations, success is a few decades down the road.”** Dyson thought it likely that we will discover evidence of extraterrestrials within 100 years. However, warned Clarke, if we have found no sign of alien intelligence after centuries of listening and looking, we might be justi- fied in assuming that we are alone in the universe.” MacGowan and Ordway addressed an even longer timescale. “Within 1,000 years from now at the most we should be able and desirous to inau- gurate a massive search program, including the use of interstellar probes if necessary, to determine the occurrence of communities out to at least 1,000 light years. If we find no evidence of extrasolar life we may well become discouraged and give up.”*” A NASA workshop report presented the issue more ambiguously. Lacking any detection, the conviction of our uniqueness would hardly ever reach certainty. It would form, over a long time, less into sharp conclusions than into a kind of substructure of human thought, a ruling consensus of attitudes*'—perhaps like the ruling consensus that preceded Copernicus aed Oat. and Galileo. Steven Dick wondered whether a century from now the search will be seen as just a curious episode in the history of science. Sociologist William Bainbridge had raised a similar question about space exploration and uti- lization in 1976: “Either spaceflight will be proven a successful revolution that opened the heavens to human use and habitation, or it will be proven an unsuccessful revolution that demonstrated in its failure to the limits of technological advance.” Thirty years later, the share of our treasure that we spend on our space efforts has been scaled down. Yet, we still send humans and machines into space; we still formulate expansive plans for the future. Like the earlier, canal-inspired search for life on Mars, the current search for radio signals may be a case of astronomers trying to resolve a problem beyond the limits of the science of their time. Yet, the conse- quences of success are so momentous that we and our descendants are likely to continue searching. If finding evidence of extraterrestrial intelligence proves to be beyond our present technical abilities, we may be justified in assuming that future humans will be capable of more. Modern science is a cumulative enterprise, Rees reminded us. Discoveries are made when the time is ripe, when the key ideas are in the air, or when some novel technique is exploited.* History tells us that the quest for cosmic company is a recurrent cultural phenomenon. Even if set back momentarily, it is likely to reappear in one form or another. Should We Continue the Search?