Word: planetful
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...Shoemakers chart the asteroids' travels, astronomers at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., hunt for another elusive creature of the night: the legendary tenth planet, or Planet X. They comb through the tangled statistics and images transmitted in 1983 from the now defunct orbiting Infrared Astronomical Satellite (I.R.A.S.), struggling to find a single pinpoint source of radiation that over a six-month period has shifted in a particular pattern among the fixed stars, as only a nearby planet can do. Says Daniel Whitmire, a University of Southwestern Louisiana astrophysicist who is involved in the search: "There...
...part of the controversy and ferment that have been bubbling through the scientific community since the rise of a spectacular new theory that attempts to explain the mass extinctions--most notably the one in which the dinosaurs perished--that have punctuated the history of life on this planet. Every 26 million years or so, the theory holds, a rain of comets that lasts hundreds or thousands of centuries bombards the earth. The impact of some of the larger comets spews enough debris into the atmosphere to block the sun for months. As the skies darken, temperatures on the ground plummet...
...meet all the other requirements imposed on it by the Louisiana scientists, Planet X would have an orbit that is elongated and highly inclined and a mass one to five times that of the earth. In other words, their Planet X is remarkably similar to the one that could account for the irregularities in the orbit of Uranus. The beauty of the theory, in Whitmire's view, is that it relies on a planet originally proposed for reasons that have nothing to do with mass extinctions. Still, he admits, the proof of the pudding "is going to come...
...celestial barrages. Some suggest that a companion star to the sun periodically comes close enough to nudge comets gravitationally out of their natural habitat--a cloud of comets that circles the sun far beyond the orbit of Pluto--sending them hurtling toward earth. Others assign that role to Planet X, while some insist that the slow, bobbing ride of the sun and its planets around the Milky Way galaxy is responsible. Whatever the details, declares Paleontologist J. John Sepkoski Jr. of the University of Chicago, the evidence for periodic mass extinctions "very strongly implicates an extraterrestrial mechanism...
...evidence of destruction, scientists could not figure out where the eraser was hidden. Geologists naturally looked to the earth for explanations, citing changes in climate or sea level. By the mid-1960s, scientists had concluded that the planet's tectonic plates are continually on the move, bumping and grinding against each other to produce earthquakes and mountains, or separating to tug apart land masses and rearrange the oceans. When sea levels change, they reasoned, animal habitats in low-lying areas may be destroyed, or the climate farther inland may grow more extreme...