Friday, August 11, 2006

Urban astronomical myths -- again

It's the astronomical e-mail spam that won't die. "Tell your children, your grandchildren!!! By August 27, Mars will look at large as the full moon to the naked eye. Never again in your lifetime or theirs will Mars look so big and bright. Etc. Etc."

The message has been making the rounds at least since the summer of 2003, when it bore a germ of truth. In that year Mars was closer than it had been since 57, 617 B. C., but only minutely so. Only a skilled skywatcher would have noticed a difference between Mars in that year and Mars in any of its every-other-year oppositions (when the Earth catches up and passes Mars in their orbits).

At its nearest, Mars is only about 1/100th the diameter of the full moon and about 1/10,000th as bright. This is an off year for Mars. We are on opposite sides of the Sun, and the Red Planet is disappearing in the evening twilight. It will be December before we again have a chance to see Mars, as the dimmer of a triad of planets -- Mercury, Jupiter and Mars -- low in the morning sky. The current rash of e-mails will send folks on a wild goose chase.

The question is not where these messages come from, but why we have such an appetite for the presumed exceptional. Why do we hanker for the unusual when the commonplace is so endlessly satisfying? Hardly a day or night goes by that doesn't offer up something in the sky that is worth dragging the grandchildren out to see. As I write, early on Thursday morning, an almost full golden moon slips behind Mount Eagle, itself slathered in pink cloud.