Fear of The Big Whopper

WHAT'S THE WORLD COMING TO? FIRST, ASTROPHYSIcists said comets killed the dinosaurs. Then they implicated asteroids in numerous other mass extinctions throughout the earth's history, setting the stage for the awful news in October that the comet Swift-Tuttle might crash into the planet in the year 2126.

The buildup to astronomical apocalypse grows ever more dramatic. At the American Geophysical Union's meeting in San Francisco, some respected researchers suggested that a large space rock 10 to 20 km (6 to 12 miles) in diameter slammed into the earth 250 million years ago and set whole continents adrift. The announcement by Michael Rampino of New York University and Verne Oberbeck of NASA-Ames Research Center stunned fellow scientists, though many dismissed it out of hand. Some skepticism seemed warranted. Rampino and Oberbeck rely heavily on their supposition that certain rocks -- known as tillites and long thought to be formed on the earth by glaciers -- were actually the result of a celestial collision. But tillites are so common that other researchers scoffed at the idea.

Finally a bit of good news: some astronomers have revised calculations on Swift-Tuttle, and predict that the big comet will breeze by us at a comfortable 15 million-mile distance. Of course, there is always the possibility that some other uncharted space rock may come crashing through the atmosphere. Best keep an eye out.