Hello dialists, Yesterday, I was able to tell the time by noting the position of a rare Tucson rainbow!
I was washing the dishes and looking out the north facing kitchen window around midday (I didn't know the time exactly though), and saw the beautiful arch of a rainbow low near the horizon. I thought that's odd, because whenever I've seen a rainbow, it's been in the afternoon or morning when the sun is low in the sky. (The reason you only see rainbows when the sun is low is because when you view a rainbow, the sun is located directly behind your head. A line drawn from the sun through your head leads to the center of the circle of which the rainbow is just a segment. If the sun is too high in the sky, the rainbow disappears below the horizon. This is why you can often see a complete circular rainbow from an airplane because there are raindrops below the plane. On the ground there are only raindrops above you). The reason I could see a rainbow at midday is because the sun is low in the sky at midday only near the winter solstice! This pushes the visible part of the rainbow up above the horizon. This rainbow geometry means that the center of the rainbow lies directly below the crest or the top of the rainbow. Therefore the crest of the rainbow is located at the same azimuth as the sun plus 180 degrees. Anotherwords, if the sun is due south then the rainbow's crest is at due north. Now, I already knew the exact location of north on the horizon from previous experience and could therefore guesstimate the position of the north/south meridian. Using my hand as a degree measurement tool, I saw that the rainbow crest was located 15 degrees west of due north. That meant that the sun was located 15 degrees east of due south. If the sun moves towards the west at 15 degrees per hour, then it must be an hour before high (apparent) noon. In Tucson, high noon is at 12:24 because of longitude correction. The rainbow said that it was an hour before high noon, or 11:24 (more or less because I didn't correct for the Equation of Time). And guess what, I turned around and looked at the kitchen clock and it said 11:30!!! Makes washing those dishes a little more fun! John Carmichael Tucson AZ p.s. Does this mean that earth is itself a sundial, and the raindrops are the gnomon?
