For 30 years the prevailing theory has been that T. rex and its brethren were wiped out by a comet or asteroid crashing in Central America, kicking up so much dust and ash that the Earth cooled for years afterward and made survival impossible.

Or was it really that simple? Some scientists, digging into well-preserved layers of the earth, said the timing was off. Yes, there is a 110-mile-wide crater, called Chicxulub, in the Caribbean off the coast of southern Mexico -- but radioactive dating suggested it was made 180,000 years after the last dinosaur fossils. Something was wrong.

So Paul Renne, an earth scientist at the University of California, Berkeley, decided to test the theory. Today he and his team report in the journal Science that the death-from-the-sky theory holds up after all. The great impact happened 66,038,000 years ago -- within 30,000 years of the dinosaurs' extinction. When you're talking about things that happened tens of millions of years ago, that's pretty good.