Word: earthly
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Dates: during 1980-1989
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...quantity of equipment that would have to be put into space. The hardware would vary enormously according to what types of weapons were selected for deployment. It makes a big difference, for example, whether laser beams are generated by millions of pounds of chemicals aboard satellites or produced on earth and bounced off mirrors in space...
Meteors, which are asteroids or cometary debris that has entered the atmosphere, continually shower the earth. Most of them are small and either break up or are burned to ash by frictional heat generated by their plunge through the atmosphere. But, explains Shoemaker, the incineration of larger asteroids is far more violent. An asteroid 80 ft. across, striking the atmosphere at 50,000 m.p.h., compresses the air in its path so much that in effect the asteroid is stopped dead in its tracks, converting kinetic energy almost instantaneously into heat, light and a powerful shock wave. That causes a tremendous...
Since 1973, Shoemaker has been photographing the sky in search of asteroids that periodically cross the earth's orbit and thus pose the danger of a collision. To date, he says, 57 such asteroids at least 1 km (.62 mile) in diameter have been cataloged. In addition, about three earth-crossing comets are detected each year. From the rate at which new earth crossers are discovered, Shoemaker estimates that there are some 2,000 asteroids in this category and that 100 comets intersect the earth's orbit every year...
...even greater menace lurks in the darkness of space. Scientists have speculated that objects as large as several miles across have crashed into the earth, spewing millions of tons of debris into the atmosphere, blotting out the sun for months or years, and causing mass extinctions of life--including, many believe, the dinosaurs. Of the known larger earth crossers, none seem to pose a threat in the near future. But, says Shoemaker, "until we have tracked all of them, something could sneak...
What if a large asteroid or comet is discovered heading toward the earth? At the AGU meeting, Shoemaker and Colleague Alan Harris, of the Jet Propulsion Laboratory in Pasadena, Calif., suggested that the intruder could be diverted by landing a thrusting device on it. As a last-ditch effort, they say, a small nuclear warhead could be detonated on or near it. Says Shoemaker: "We have the technology to do that right now." But if the explosion simply broke the meteorite into large chunks, the danger would only be multiplied. "The more prudent solution," says Harris, "is to burrow...