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Where are the Extraterrestrials Hiding?
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13021 |
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Section : |
NATURAL SCIENCE
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| Issue
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5 / 1987 |
2,258 Words |
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Seth Shostak
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According to Hollywood, the universe beyond Earth is populated by only two types of alien creatures: the good and the bad. The white hats among the extraterrestrials usually make contact with earthlings reluctantly, as did the Antarean rescue team in Cocoon, or accidentally, as in the unintended abandonment of E.T. But once in touch with the earthlings, these often anthropomorphic aliens help us out by promoting peace, improving our health, or simply amusing our children. When they leave - and the good aliens always leave - we wave them goodbye with a thankful tear in the eye.
While benevolent extraterrestrials may have the current upper hand at the neighborhood cinemas, it was not long ago that, to paraphrase John Wayne, the only good alien was a dead alien. Inspired by conquest, hunger, or just plain orneriness, the bad guys from space destroyed our cities, devoured our space explorers, took over our bodies, or engaged in endless interstellar battles with our descendants.
Drama depends on antagonism, so it is hardly unexpected that Hollywood has so sharply categorized the denizens of deep space. But surprisingly enough, the temperament of the extraterrestrials has lately become a matter of scientific interest.
Concern for the true nature of extraterrestrial behavior derives from the continuing failure of a small, back-burner scientific enterprise. For several decades now a limited number of countries, including the superpowers, have expended both scientific manpower and money on the Search for ExtraTerrestrial Intelligence (SETI). While long a matter for speculation, the question of the existence of alien beings has recently become fashionable for good reason: The development of radio astronomical techniques since World War II has finally provided an effective means for detecting the extraterrestrials.
The method used is simply to electronically "eavesdrop" on any radio signals that might be deliberately or accidentally beamed our way. Large radio telescopes, which are nothing more than highly directional antennas, are trained on nearby stars considered to be good candidates for harboring Earth-like planets. Radio signals received by the telescope are then analyzed for any unnatural behavior - a pattern of pulses, for example - that would betray an intelligent broadcaster. There are endless technical nuances to this apparently simple scheme, as scientists try to second-guess extraterrestrials regarding the likely choice of transmitting frequencies, speed of transmission, and so forth. But the bottom line of two decades of search is a negative result. No convincing sign of life has been heard.
Assessing the paradox
Given the mammoth technical difficulties involved, it may be premature to attach any significance to this failure, and yet many astronomers are already uncomfortable. Our galaxy alone consists of several hundred billion stars. If only a small fraction harbor life-bearing planets, then the number of intelligent civilizations dispersed throughout the Milky Way could be a million or more. Some of these presumably would have had time to develop the technology of interstellar rocketry.
Now, the followers of Von Daniken may believe the aliens have been here, and the UFO crowd thinks they still are, but most
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