Colors of the Moon

My friend Sally James (aka Dr. Sara James, Professor of Art History at Mary Baldwin College) visited me this past weekend, fresh from a week-long seminar in New York about scientific techniques for analyzing and dating works of art. I had been Sally's house guest in Staunton, Virginia, for most of May, when I taught a short course in "Writing Creatively about Science" for Mary Baldwin students. The planets Mercury, Venus, Mars, and Jupiter were clustering in attractive dawn patterns during much of my stay, but every time we set our alarms early to observe them, the weather foiled us. As consolation, I suggested Sally fan her interest in astronomy by starting a Moon journal: She would look for the Moon every day and night; write down where and when she found it, and describe how it looked in those moments.

The following month, while on vacation at Wrightsville Beach, North Carolina, Sally got two of her granddaughters to keep Moon journals, too. On the evening of June 15, while a lunar eclipse unfolded over parts of Africa, the Middle East, central Asia, and western Australia, Sally saw the full Moon rise out of the Atlantic looking as red and gold as autumn leaves. She took several photos of it.

Having heard that the Moon turns red when submerged in the Earth's shadow, she wondered whether the color she'd captured with her camera had anything to do with the night's big event on the other side of the world.

In fact the Moon as viewed from North Carolina owed its redness to effects entirely unrelated to the eclipse. Just as the Sun glows reddish near the horizon at sunrise or sunset, the Moon, too, may blush while rising or setting, as its light (the sunlight reflected by the Moon's surface) travels through the thick, dust-laden lower atmosphere. The ocean mists may also contribute a reddening effect. Sally's later photos showed how the Moon whitened when it climbed higher into the sky.

We had a "new Moon," meaning "no Moon visible," for Sally's brief stay here. We sat outside till late on her last night, watching the Milky Way, counting occasional meteors even as lightning flashed in the west.