Earth and Moon Comparison

November 05, 2012

Earth and Moon

Photographer: David K. Lynch; Dave's Web site 
Summary Author: David K. Lynch

How different the Earth and Moon look from each other by day! From the airless Moon, the Earth appears clear and crisp against a black sky. From the Earth, the Moon shines pale and indistinct, being flooded with blue light from the sky. Most of the difference is due to the Earth’s atmosphere, especially when the Moon is low on the horizon. Here the sky is bright and atmospheric extinction causes the Moon to appear fainter. But other factors play a role. The reflectivity (Bond albedo) of the Moon is 0.12, or 12 percent. The cloud-free Earth’s is 0.29. Clouds and snow can brighten the Earth considerably, something that cannot happen on the Moon. The Bond albedo of fresh snow is about 0.84, and that of thick cumulus clouds is around 0.78. These brightness variations cause the earthshine, light reflected from the Earth to the Moon and back again, to change from month to month.
Left: NASA photo by Apollo 8 crewmember Bill Anders on December 24, 1968. Right: Photo by the author from Topanga on October 2, 2012.