Tuesday, December 26, 2006


A rainbow last evening, and another this morning. I have seen as many as four bows in a single day here in Exuma. Morning and evening showers tend to sweep swiftly across the islands, with clear intervals between -- ideal conditions for rainbows.

I have made something of a hobby of predicting bows. "There'll be a rainbow just over there," I'll say to whoever is in my company, with an arching sweep of my arm, "in six minutes time." I am seldom wrong.

The trick never fails to astonish, but it's not hard to do. After watching me do it often enough, my spouse has picked up the habit. "Rainbow alert," she'll shout, and we run to the terrace to see if she's right. Yep, there's the bow.

Fred Schaaf, the astronomy popularizer, sometimes calls people on the telephone to tell them a rainbow is heading their way.

Of course, that's only a matter of speaking. Rainbows don't exist out there, like a cloud or an airplane. They exist only on the retina of an observer's eye, and every observer has a different posture with respect to rain and Sun. What is moving down the telephone line are the meteorological conditions that are likely to produce a bow: direct light from a low-altitude Sun and mist or rain in the opposite part of the sky.

Perception, writes Diane Ackerman, is a form of grace. In Catholic theology, one must be predisposed to grace to receive it.