Saturday, February 26, 2005

Faint lights

For the next few nights I will be looking for the zodiacal light, a band of faint light reaching up along the band of the zodiac from the western horizon after the Sun has set. It is caused by sunlight reflecting from the swarm of micrometeoroidal particles that dusts the plane of the solar system, orbiting the Sun like a myriad of microscopic planets. (After the planets formed, the cosmic dustmaids didn't do a very good job of tidying up.)

Late February is the best time of the year to see the light, because the ecliptic (plane of the solar system) is steeply inclined to the horizon, lifting the light above the haze. Being in the tropics helps too; the ecliptic doesn't get any steeper than here. And the moon is now rising late enough to have a dark sky for a few hours after sunset.

This island used to be very dark, and I've seen the zodiacal light many times from here. But as the island develops and lights come on, one more of nature's subtle wonders is slipping into invisibility.