December 31, 2009
Already 99.9 (and about 58 more 9s) percent of the universe — it is expanding lickety-split — is beyond Earth's atmosphere. Into what is it expanding? Hard to say. We can say there is lots of stuff in space: Hold up a penny at arm's length and you block from your field of vision three galaxies — billions of stars and other things — 350 million light-years away, which is right next door in our wee corner of the universe.
But there is much more space than there is stuff in space: If there were only three bees in America, the air would be more crowded with bees than space is with stars. But there is much stuff besides stars whizzing around, and 65 million years ago — the day before yesterday on the calendar of the 14 billion-year-old universe — big bits of stuff entered Earth's atmosphere traveling faster than a high-caliber rifle bullet.
One result was a 16,000-foot mountain, Bombay High, that has never been climbed because it is underwater off India's west coast. Another result was the ''worldwide collapse of the climate and ecosystems'' leading to the mass extinctions of the dinosaurs and two-thirds of marine animals, and the destruction of much of the planet's flora. So surmises Sankar Chatterjee of Texas Tech University.