Moonlight

Night before last we were heading home late and the moon was rising. It was near the horizon and looked huge. It was a half moon, "on its back", like a big orange slice. The beauty of the phases of the moon is one of the blessings available to every earthling. The cold science of the moon's motion and appearance has nothing to do with aesthetics, but we who live here love the moon. Flowing water, trees, clouds, mountains, moss, desert sunsets - we love it all, and are so often cut off from all this beauty by our houses and electric lights.

Moonlight is silvery. Why? Bright as the full moon looks, it is about 500,000 times fainter than the sun (http://en.wikipedia.org/wiki/Moon_light). Our eyes are cleverly designed to work in both bright light and dim, and all between. Have you ever noticed how, as the light fades, the landscape gradually seems to lose color. Reds fade out first, turning blackish. Then the other warmer colors go, leaving blues and greys. Finally, by moonlight, there is no color we can distinguish - just a scene of shades of grey. This is because our retinas are made up of two different kinds of receptors - the rods and cones. The cone cells are the ones that see color, and they do not function at low light. The rods are very sensitive. They are located near the edges of our retinas and help with peripheral vision, but they don't see color.

So our night vision sees a silvery scene by moonlight - and we find it beautiful.