The New and Old Moon

In a clear colorful dusk the young crescent moon stands above Gulf of Oman from southeast Iran. Click the second photo to see a close-up telescopic look to the crescent moon, this time an old moon in morning sky. Featured on Astronomy Picture of the Day, the image shows the Moon’s ashen glow or Earthshine, the Earthlight illuminating the Moon’s night side. The darker earthlit disk is in the arms of a bright sunlit crescent. But the view from the Moon would have been enchanting too. When the Moon appears in Earth’s sky as a slender crescent, a dazzlingly bright, nearly full Earth would be seen from the lunar surface. The Earth’s brightness due to reflected sunlight is known to be strongly influenced by cloud cover. Still, a description of Earthshine, in terms of sunlight reflected by Earth’s oceans in turn illuminating the Moon’s dark surface, was written 500 years ago by Leonardo da Vinci.