Word: alvarez
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...Alvarez, his curiosity aroused, shipped samples of the sediment back to the U.S. and showed them to his father Luis, a Nobel-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...
Journeying to Denmark, another site where the Cretaceous geological record is complete, Walter Alvarez gathered corroborating samples of iridium and received still more from colleagues working at a third site on the other side of the world, in New Zealand. The evidence seemed overwhelming. In 1980 the Alvarez team finally published its results in the journal Science and stirred up some scientific debris of its own. Says Paleontologist Leo Hickey, director of the Peabody Museum of Natural History at Yale: "My first thought was this is one of Walter's practical jokes...
Other scientists, drawn into the fray by the Alvarez conjecture, have since suggested that a large comet might have similar consequences. Los Alamos Weapons Experts Stirling Colgate and Albert Petschek computed that a comet six miles in diameter hitting the earth would have an effect 100,000 to 1 million times as great as a large nuclear explosion, and would blow a 100-sq.-mi. hole in the atmosphere...
...glass called microtektites, which form in rock when something hits it with great force--further evidence of a major collision. Yet investigators continued to regard the findings from the two time periods as being no more related than, say, separate automobile accidents in Des Moines and Miami. Explains Walter Alvarez: "It seemed to everybody involved that extinctions and impacts should be random in time...
...Before publishing their report, Muller decided to get a second opinion from the fathers of the impact theory, Luis and Walter Alvarez. Neither conferred his benediction on the hypothetical star, but Walter recommended one way that its existence might be tested. He knew that if comets cyclically pelted the planet, they must have left behind craters in chronologically distinct batches. Water, wind and continental drift have eroded 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...