Word: asteroids
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...world may someday end with a whimper, but evidence is mounting that the dinosaurs went out with a bang. According to the much debated theory proposed by the father-son team Luis and Walter Alvarez in 1980, an asteroid or comet slammed into the earth at the end of the Cretaceous period, 65 million years ago, spewing so much dust into the atmosphere that sunlight was blocked for months. Temperatures plummeted, plants withered, and many species, including the mighty dinosaurs, perished en masse...
...Clemens' view, the discovery indicates that at least some dinosaur species were not sensitive tropic dwellers but were able to survive through chilly and dark Arctic winters lasting from November to February. That theory tends to undermine the currently popular asteroid version of the apocalypse. According to that model, all dinosaurs perished when an asteroid or comet collided with the earth and tossed obscuring dust into the air, blocking sunlight and lowering ground temperatures. Clemens counters that dinosaurs living up north would hardly have noticed the difference, let alone be wiped out. Says he: "It doesn't matter if your...
...about stars and periodicity, when Muller noted that more than half the stars in the galaxy are thought to be binaries (pairs of stars that orbit a common center of gravity). Suppose the sun has a companion, he mused, and that companion was somehow disrupting the solar system's asteroid belt. Trouble was, he conceded, he could not come up with a convincing orbit for the companion. Suddenly the Dutch-born Hut interrupted him with an alternative suggestion: Why not make the companion star travel through the thickest part of the comet-filled Oort cloud, rather than the asteroid belt...
Although both comets and asteroids can wreak considerable havoc if they collide with the earth, they are of very different natures and origins. Asteroids are rocky chunks that range in size from pebbles to a mammoth named Ceres that astronomers estimate to be as much as 600 miles across. Most of them orbit the sun in a belt between Mars and Jupiter and are thought to be either remnants of a planet that disintegrated early in the life of the solar system or celestial building blocks that never quite coalesced into a planet. Occasionally an asteroid is slowed...
Even now, more than three-quarters of a century after the spectacular event at Tunguska, scientists are certain only that a celestial intruder was responsible. Some argue that it was an asteroid as large as 500 ft. across and weighing 7 million tons, which rapidly heated as it entered the earth's atmosphere and exploded about five miles above ground. Others believe it was a small comet. Whatever the cause, the destructive power of the object from space rivaled that of a very large nuclear warhead; scientists gauge the explosion at twelve megatons...