How to see moon’s ‘Da Vinci glow’ this week as phenomenon threatened by climate crisis

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Andrew Feinberg

White House Correspondent

A lunar phenomenon called the “Da Vinci glow” which lights up the unlit side of the moon, is expected to be visible from Earth this week and over the coming weekend.

The process, also called Earthshine, is a faint glow of the moon’s shadowed “dark” side due to sunlight reflecting off the Earth’s surface and back onto the moon.

This dull glow is visible only on a slim crescent lunar surface when the moon is close to the horizon during both the last few days and the first few days of its orbit around the Earth.

The main source of the moon’s faint glow during this time is the light reflected off the Earth’s clouds and sea ice, according to Nasa.

It is named after Italian polymath Leonardo da Vinci, who explained the phenomenon for the first time in the 15th century.

Space experts said this weekend is a good time to spot the faint glow on the moon.

The intensity of Earthshine varies in strength over the course of a year as light reflected from the Earth varies.

The albedo, or Earth’s reflected light, is the brightest during the Northern Hemisphere spring, with a slightly smaller peak happening in the Southern Hemisphere spring.

This is because, during the Spring season in the Northern Hemisphere, the Earth is tilted towards the sun and winter snow and ice are still around.

And since snow and ice reflect more light, Earthshine is brighter during this time of the year as compared to the winter when the Arctic receives very little light from the sun.

People on Earth might see the Da Vinci glow a few days before the new moon on 19 May, and for a few days after – given the skies are clear – according to timeanddate.com, a portal for checking different times and time zones.

In the eastern sky, people may see the phenomenon in the hour leading to sunrise on 16 and 17 May and on the western side, skywatchers may witness the Earthshine on 21-23 May, about an hour after sunset.

During these times, experts predict the reflected light off Earth could likely be about 10 per cent brighter.

In recent times, the warming of the Pacific Ocean is linked to a reduction of low-lying cloud cover and thereby the proportion of sunlight reflected from Earth.

A study, published in 2021 in the journal Geophysical Research Letters, found Earth was reflecting less light back on the surface of the moon’s dark side due to the warming, affecting the Earthshine phenomenon.

In the 1998-2017 period, researchers found the amount of light reflected from the Earth dropped by 0.5 per cent.

This corresponds to a reduction of about half a watt of light per square metre over two decades.

The trapped solar radiation could warm up the ocean further and may lead to further Earthshine reduction, experts said.