TV Beacons in Space

The ultrahigh-frequency television stations that are gradually spreading across the country may be reaching an unexpected audience. UHF transmissions, says Institute of Electrical and Electronics Engineers President Bernard Oliver, may have already provided the first evidence to extraterrestrial civilizations that intelligent, or anyway TV-producing life exists on earth.

Sweeping the Universe. Unlike low-frequency radio waves, which are reflected back by the earth's ionosphere, UHF transmissions continue traveling in a straight line out into the farthest reaches of space. And unlike standard television waves, which penetrate into space but tend to be drowned out by cosmic radiation of about the same frequency, UHF broadcasts could eventually be detected as far off as 200 light years from earth. Each UHF station, says Oliver, sends out its signal in a thin, disklike pattern tangent to the earth. As the earth rotates, that disk sweeps the universe like a giant beacon, eventually carrying its UHF transmission past stars and planets many light years away.

With a sensitive receiver tuned to the UHF frequency of about 670 megacycles, for example, non-earth beings might first detect the signal of an East Coast city's channel 47 as it fans across their distant planet. The rotating earth would bring the signal of a Midwest channel 47 into range about two hours later, a California channel 47 about three hours after the East Coast signal. Not that the observers far in space would be able to distinguish the educational, news and entertainment programs that were shown last week; but they would probably be able to detect such man-made patterns as the synchronization signals transmitted by the station.

An Antenna Orchard. A receiver capable of picking up such distant signals is already within the technological capability of man, Oliver believes. He proposes an array of 10,000 dish antennas, each 100 ft. in diameter. With such an enormously sensitive radio telescope, he says, astronomers would be able to pinpoint the faintest radio signals coming down from space.

The cost would be astronomical--as much as $5 billion. But the instrument could advance the infant art of radio astronomy to a rewarding maturity that might produce more scientific discoveries than the $40 billion program to put a man on the moon. And if while using their powerful instrument radio astronomers pick up a hint of an intelligent pattern in UHF signals from space, Oliver says, "an age-old question will have been answered. We will know that we are not alone."

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