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The Da Vinci glow, also called Earthshine, is when light reflecting off our planet illuminates the outline of a full moon.
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Look up at the sky next week, and you might catch a glimpse of the Da Vinci glow.
This is a phenomenon that can occur around sunset when a crescent moon is on the horizon, but the outline of a full moon is visible. The Da Vinci glow is a common phenomenon, and easy to spot, says Christine Shupla, the science engagement manager at the Lunar and Planetary Institute in Houston. But its appearance was once an inscrutable mystery.
What causes the ghostly full moon effect, sometimes called “the old moon in the arms of the new moon,” is an ancient question that was elucidated by Leonardo da Vinci, according to NASA. And the answer is the light reflected from the Earth to the moon.
Different from sunlight, Earthshine refers to the light from the sun that the Earth reflects even after the sun has set, NASA said. Earthshine is about 50 times brighter than the light from the full moon.
Different from sunlight, Earthshine refers to the light emitted from Earth even after the sun has set, NASA said. This source of light coming from Earth is about 50 times brighter than the light from the full moon.
When Leonardo theorized about this, Copernicus had not yet published the theory that the Earth revolved around the sun. But through an artistic understanding of light and shadow and an engineer’s understanding of geometry, Leonardo was able to determine where the ashen glow around the crescent moon came from, NASA said.
Leonardo was right about the Earth reflecting light to see the moon’s outline, but the Apollo 11 astronauts in 1969 learned more. When the astronauts peered down at Earth, the light was not reflected by the oceans, as Leonardo thought, but by the clouds, NASA said.
Anyone with a view of the moon can see the Da Vinci glow, but conditions have to be right for it to happen, Shupla said.
“Easiest to see during a waxing or waning crescent. You’ll need clear skies to see the Moon, but parts of Earth need to be cloudy enough to reflect enough light onto the Moon,” Shupla said in an email.
“Sky watchers should look for the banana-shaped crescent Moon at night around sunset, and try to see the rest of the Moon, which is partially lit,” Shupla added.
Correction: A previous version of this story incorrectly identified Earthshine.
