Wednesday, July 05, 2006

One never knows

Antoine de Saint-Exupery's Little Prince lives on an world so small he can watch a dozen sunsets in a single evening just by moving his chair westward around the circumference of his tiny planet. His planet has three volcanoes, two active, one extinct; he keeps the active volcanoes tranquil by periodic cleaning with a Q-tip sort of swab.

It would be cruel to turn the cold eye of science on so charming a tale, so I will not point out that the Little Prince's tiny planet would have too little gravity to retain an atmosphere, or for that matter a prince. Or that so small a planet would have long since lost whatever internal heat might cause an untended volcano to erupt. But this much is true: There are lots of tiny planets in our solar system that would make perfect habitats for imaginary princes.

A half-mile wide minor planet gave the Earth a near miss on Monday, passing just 269,000 miles away, slightly farther than the Moon. A quarter-of-a-million miles may sound comfortably removed, but it's roughly equivalent to a stray bullet passing within 20 feet of your head. You wouldn't want to take that risk every day. If something that size hit us it would be very serious businesss indeed.

These kind of things are flying all around out there. It is inevitable that now and then a good-sized object will hit the Earth; the planet is pocked with the scars of former collisions. It doesn't pay to dwell too long on the subject, since threre is nothing we can do about it. A catastrophic collision could happen today or not for thousands of years.

The Little Prince faithfully cleans even his extinct volcano. "One never knows," he says. The advantage of fantasy over science is that we are allowed to think the universe tidier and safer than it actually is.