Fifty years ago, an American astronomer called Frank Drake started to search for signals coming from alien civilizations. Paul Davies, a British physicist, examines in a new book why it might be that mankind has not heard from extraterrestrials, the significance of this lack of response, whether might yet make contact and how people might react to them. The short answer is: no one knows.
The universe is immense, which makes many scientists confident that life might have evolved elsewhere. Perhaps, concedes Mr. Davies, but for life to signal its existence, it must be intelligent, which whittles things down a bit, and it must have developed science, which further slims the chances. Moreover, because the universe is so vast, it takes years for signal traveling at the speed of light to reach only as far as the next star to our sun. Modern man evolved as a species 100,000 years ago but began broadcasting his existence less than 100 years ago. If mankind were, this week, to receive a reply from extraterrestrials that had tuned in to the earliest broadcasts, they must be living less than 50 light - years from the Earth. That is a tiny pocket in the universe. No surprise, then, that so far nothing has been heard.
Mr. Davies points out that scientists who search for aliens using radio telescopes are assuming that other life would use this form of communication. But people are increasingly using the internet to talk to one another. Within the next 100 years, mankind may no longer use radio. Astronomers are using the only tools at their disposal but these may well be the wrong ones for the job.
Of course, there is the possibility that intelligent, scientifically minded alien species do evolve quite readily on extra - solar planets. This would be threatening for humanity, and is what makes the silence eerie. The lack of contact would suggest that intelligent life and technological civilizations maybe inherently unstable, and destroy themselves before they can signal their existence to one another.
Given the great size not only of space but also of time, perhaps intelligent life looks different elsewhere. If mankind persists for a further 10,000 years, the species will surely change. Indeed, it has already developed intelligent machines and is well on its way to building devices that are more intelligent than their makers.
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