Word: occured
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Dates: during 1980-1989
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Moreover, it is the responsibility of all members of the academic community to maintain an atmosphere in which violations of rights are unlikely to occur and to develop processes by which these rights are fully assured. In particular, it is the responsibility of officers of administration and instruction to be alert to the needs of the University community; to give full and fair hearing to reasoned expressions of grievances; and to respond promptly and in good faith to such expressions and to widely-expressed needs for change. In making decisions which concern the community as a whole or any part...
...theory is correct, the next catastrophe will not occur for at least 13 million years. But the effect of the new concept on science and scientists has been much more immediate. One measure is the ferocity of debate it has generated in the past few months among eminent researchers, at conferences and in the letters-to-the-editor columns of major newspapers and staid journals alike. Supporters of the Milky Way proposal dismiss the Nemesis notion as "unlikely" and "ad hoc," and death star advocates are scornful of the galactic concept. Many consider all the newfangled extraterrestrial scenarios...
...prizewinning physicist also at the University of California, who had the clay analyzed. To everybody's surprise, it turned out to be 30 times as rich in iridium as normal rocks. The Berkeley team knew of only a few places where such high concentrations of the rare element might occur: in the earth's core, perhaps 2,000 miles belowground; in extraterrestrial objects like asteroids (or their fragments, meteors) and comets; or in the cosmic dust drifting to earth from a nearby supernova (exploding star). The core material seemed too deep to come to the surface, and further analysis ruled...
...most of the earth's impact craters, but 100 of the largest survive in some form and have been roughly dated. Muller and Walter Alvarez examined the data on 13 of the best- dated craters spanning a period of 250 million years and, sure enough, the gutting seemed to occur in peaks of 28.4 million years (although the later inclusion of data from other craters made the pattern seem less conclusive...
...solar system or celestial building blocks that never quite coalesced into a planet. Occasionally an asteroid is slowed in its travels, probably by the gravity of nearby Jupiter, and tugged into an orbit that sends it closer to the sun and the inner planets, including earth. And sometimes collisions occur. About 100 of the earth's largest known craters are believed to have been caused by huge asteroids dropping from the heavens...