Earthshine: Earth Illuminates Moon with Ghostly Da Vinci Glow

The ghostly Da Vinci glow, formerly known as Earthshine, proves that the Earth can also light up the moon.

This week, those who glance up at the night sky may notice a hazy, spectral glow illuminating the entire moon.

Earthshine and the Ghostly Da Vinci Glow

Known as the "Da Vinci glow," the phenomenon is named for the inventor and artist Leonardo Da Vinci. The Renaissance-era artist also sought to unravel the enigma of what was originally referred to as "Earthshine," according to NASA.

Only a crescent moon on the horizon at either sunrise or sunset makes the celestial occurrence observable. The moon's crescent sparkles brilliantly during the occurrence, and its dark side appears as an overcast. The radiance is not a result of the moon shining on its own. It is produced by planet Earth, whose light can brighten the night sky by a factor of 50, compared to the brightness of a full moon, NASA says.

Da Vinci's Codex Leicester

According to NASA, Da Vinci set out to discover the enigma behind that eerie radiance in the 16th century. In his notebooks, he produced a drawing that seemed to depict the phenomenon; this drawing is remembered in the "Codex Leicester," a collection of the scientific writings by Da Vinci.

Like his contemporaries, Da Vinci was operating with a sketchy knowledge of the solar system. NASA claimed that it would be another 20 years before the idea that the sun is at the core of the solar system would be widely accepted, and of course, no one had ever visited the moon. As a result, little was known about how close the sun was to Earth.

Solving the Riddle

According to NASA, there is a passage in the "Codex Leicester" titled "Of the Moon: No Solid Body is Lighter Than Air." Da Vinci highlighted several theories, including the notion that the moon contains an atmosphere and oceans. He was right about the first thing, but the second thing has been proven false by NASA missions. Da Vinci also stated that the moon acted as a light reflector.

Using this knowledge, he put up a theory: Earthshine's eerie glow was caused by sunlight reflecting off the oceans of the Earth and striking the moon.

Slim Cresent Moon Days

According to Live Science, the glow can only be seen on the first or last few days of the lunar cycle when a thin crescent moon is visible near the horizon. This phenomenon can be seen on Thursday mornings at sunrise, which is a nice time to attempt and watch the event.

The next week Sunday, May 21, Monday, May 22, and Tuesday, May 23, are the best days to observe it after sunset. Try observing the sky for an hour after sunset.

According to NASA, April through June are typically the brightest months for Earthshine.

No extra tools are required to see the glow. In actuality, unassisted vision is the greatest way to perceive it. Binoculars and a small telescope are useful but not necessary, CBS News reports.