Word: earths
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Dates: during 1990-1999
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...years continental drift was held up to derision--until scientists in the 1960s found a plausible mechanism in the earth's internal motions under the ocean floor. Suddenly, Wegener's disreputable ideas became reputable. Renamed plate tectonics, they gave geology a single unifying theory, explaining everything from earthquakes and volcanoes to the formation of mountain ranges and ocean basins. Sadly, Wegener, who perished on the Greenland icecap in 1930 at age 50, didn't live...
...idea that a comet or asteroid might be bearing down on Earth--as in Deep Impact and Armageddon--can be traced to this crusading geologist. Probing Arizona's Meteor Crater in 1956, Shoemaker found a form of quartz that is created only by tremendous impacts. Finding the same telltale mineral in other craters, he concluded that they had been formed not by volcanoes, as most scientists thought, but by large objects hitting Earth. It was only a matter of time, he said, before Earth would be struck again. So he launched the first organized search for big incoming objects, recruiting...
...20th century has made science more exacting. We demand more of its explanations. To say that the earth goes around the sun is no longer sufficient; we insist on knowing why. And in some fields--space research, for example--decades can go by while novel instruments are designed and built. A further complication is that every discovery provokes new questions. The more we know, the more we do not know...
...possible for the ancestors of modern people to stand upright (about 4 million years ago) and then to speak. As a by-product, we shall be able to trace the migration routes of our human ancestors who emigrated from Africa and came to populate the surface of the earth. A half-century from now, we shall have a rich and authentic history of the human race...
...gene technology can use the DNA in every living thing as a vast repository of historical information. Even dna will not point all the way back to the beginning of life, but it will provide clues to the self-replicating entities first assembled from simple chemicals on the primeval earth. The century ahead will see the first laboratory proof that self-replicating systems can form from ordinary chemicals. Determining whether that is how life really began will take longer...