The Arc Opposite the Sun

Stand with the sun behind you and the arc will be centred on the point directly opposite it, the same point your shadow's head marks on the ground. Red sits about forty-two degrees out from that centre, violet about forty, and every colour between takes its own ring. This is why the bow moves when you walk toward it and why no two people are looking at quite the same one.

The second bow, when it appears, is fainter and reversed, red on the inside, because the light bounced twice inside each drop instead of once and lost some strength on the way. Between the two lies a band of sky noticeably darker than the rest, Alexander's band, where drops send almost nothing back to the eye. Low sun raises the arc, midday sun pushes it below the horizon entirely, which is why the good ones turn up late in the afternoon after a shower moving away.

For a photograph the colours are gentler than memory claims, and pushing saturation to fix that usually breaks the sky around them first. It helps that a bow needs rain in front and clear light behind, so the frame comes with its own drama already staged. On a screen it is one of the few subjects that reads as an event rather than a place, which makes it good company on a working day and less good as a wallpaper you intend to forget.