A crescent moon rises behind the rugged outline of the Dolomite mountains in Italy. In this photo taken on March 30, just before the moon sets at dusk with a 1-second exposure, the bright part of the moon appears very thin. The entire shape of the moon is also faintly revealed. This phenomenon occurs due to earthshine, which is light reflected from Earth.
Earthshine, also known as the moon's ashen glow, is a phenomenon that Leonardo da Vinci described about 500 years ago, noting that the light reflected from Earth’s oceans illuminates the dark side of the moon. Earthshine is a classic example of planetary reflection, where light from a planet shines on its satellite, and it is perhaps the most familiar case of this phenomenon.