“Da Vinci Glow: A Mysterious Phenomenon Explained by NASA and Leonardo’s Theories”

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Look into the sky next week, and you just might catch a glimpse of da Vinci’s glow.

This is a phenomenon that can occur near sunset when the crescent moon is on the horizon, but the outline of the full moon is visible. Da Vinci flares are common and easy to see, said Christine Schupla, director of engagement science at the Lunar and Planetary Institute in Houston. But his appearance was once a dark mystery.

What causes this phantom effect of the full moon, sometimes called the “old moon in the arms of the new moon”, is an old question posed by Leonardo da Vinci, According to NASA. The answer is the reflection of light from Earth to the Moon.

NASA says that Earth’s brightness, as opposed to sunlight, refers to the light from the Sun that is reflected by Earth even after sunset. Earth’s brightness is about 50 times brighter than the light of a full moon.

NASA says that Earth’s brightness, as opposed to sunlight, refers to the light Earth emits even after the sun has set. The light source from Earth is about 50 times brighter than a full moon.

When Leonardo theorized about this, Copernicus had not yet published the theory that the earth revolved around the sun. NASA said that through a technical understanding of light and shadow and an engineer’s understanding of geometry, Leonardo was able to determine the source of the ash plume around the crescent.

Leonardo was right about the Earth reflecting light so that the outline of the Moon can be seen, but the Apollo 11 astronauts in 1969 learned more. NASA says that when the astronauts peered at Earth, the light was reflected not from the ocean, as Leonardo thought, but by the clouds.

Anyone looking at the moon would be able to see da Vinci’s light, says Schupla, but conditions had to be just right for this to happen.

“It’s easier to see when there’s a waning or waning crescent moon. You need a clear sky to see the moon, but the part of Earth has to be cloudy enough to reflect enough light on the moon,” Chopla said in an email.

“Skywatchers should look for a banana-shaped crescent in the evening at sunset, and try to see the dim remnants of the moon,” Chopla added.

revision: An earlier version of this story misidentified Earthshine.