The Da Vinci Glow

"When you think of Leonardo Da Vinci, you probably think of the Mona Lisa or 16th-century submarines or, maybe, a certain suspenseful novel. That's old school. From now on, think of the Moon.

"Little-known to most, one of Leonardo's finest works is not a painting or an invention, but rather something from astronomy: He solved the ancient riddle of Earthshine.

"You can see Earthshine whenever there's a crescent Moon on the horizon at sunset. Thursday, Oct. 6, is a good night: sky map. Look between the horns of the crescent for a ghostly image of the full Moon. That's Earthshine.
"For thousands of years, humans marveled at the beauty of this 'ashen glow,' or 'the old Moon in the new Moon's arms.' But what was it? No one knew until the 16th century when Leonardo figured it out.

"In 2005, post-Apollo, the answer must seem obvious. When the sun sets on the Moon, it gets dark--but not completely dark. There's still a source of light in the sky: Earth. Our own planet lights up the lunar night 50 times brighter than a full Moon, producing the ashen glow ..."
NASA

Leonardo da Vinci in the Book of Days

Above: A crescent moon with Earthshine over Yosemite National Park in October 2004. Photo credit: Andy Skinner. See it embiggened.

Tagged: nasa, moon, leonardo, da+vinci, science, lunar, space