Word: planet
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Dates: during 1980-1989
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...President, you promised us a clean administration--clean planet, clean schools, clean government. After 100 days, what do we have? An oil slick in Alaska, blood-stained streets in Anacostia and mud-spattered reputations in the government, your government...
...close you came to disaster. While you were blissfully unaware of the danger, a huge asteroid whizzed past the earth, coming closer than any other such heavenly body seen in 52 years. If the giant clump of rock -- half a mile across by one estimate -- had hit the planet, it would have packed the wallop of thousands of H-bombs and possibly killed millions of people. If it had come down in an ocean, it could have triggered tidal waves hundreds of yards high...
...only in a relative sense. At its closest, the asteroid was about 450,000 miles away, roughly twice the distance between the earth and the moon. Still, in cosmic terms it was virtually a direct hit. No asteroid has been sighted so near since 1937, when Hermes, a minor planet nearly half a mile in diameter, passed by at about the same distance...
...times before, in fact, that the earth's surface would be as pockmarked as the moon's were it not for the cosmetic effects of erosion caused by the oceans and atmosphere. Half-mile asteroids are a dime a dozen in the solar system, and they run into the planet once every 100,000 years, on average. That means the next one could strike in a thousand lifetimes -- or before the end of next week...
Then there are the really big asteroids -- masses of rock and iron five or ten miles across that hit every 10 million to 100 million years. The half- milers are bad enough, but these giant ones pose a threat to the entire planet. It was such an asteroid (or an equivalent-size comet) that many scientists believe caused the extinction of dinosaurs some 65 million years ago. The primary evidence, discovered by the late physicist Luis Alvarez and his son Walter, a geologist, is a layer of the element iridium laid down in sedimentary rock at about the time...