Physics Photo of the Week

March 5, 2010

Earthshine on the Rising Moon
When we see the Moon as a crescent we often see the whole Earth-facing side dimly lit as wel as the bright crescent.  This light on the dark part of the Moon is called "earthshine".  Reflected light from the planet Earth radiates out into space and lights up the night side of the Moon.  It is the same effect as Moonshine on Earth (the light of the moon, not an illegal beverage).

This photo was taken over a year ago (January 23, 2009) when we had a clear pre-dawn view of the waning crescent Moon.  The
Moon is rising as can be seen by the animated sequence at right.  The pictures in the animation were taken once every 10 seconds and played back at 10 frames per sec - speeding up the motion by a factor of 100.  Notice that the sky is gradually becoming brighter as dawn or sunrise is approaching.  The Sun will rise in the lower left part of the picture in the approximate position of the line of the rising Moon.  On close examination of the animated picture, thin clouds can be seen passing in front of the Moon.

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to 

All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion.  These photos and discussions may be used for private individual use or educational use.  Any commercial use without written permission of the photoprovider is forbidden.

Click here to see the Physics Photo of the Week Archive.

Observers are invited to submit digital photos to: