Physics Photo of the Week

March 30, 2007

Crescent Moon and Earthshine
Crescent MoonOn December 18, 2006 I photographed this fantastic Moon rise from near Warren Wilson College.  The amazing feature about the Moon's appearance is the glow of the dark part of the moon.  This is called Earthshine - caused by light reflected from the Earth that reaches the Moon.  Think of Moonshine on Earth - a similar phenomenon in which the Earth's night side is illuminated by light from the Moon.  (See PPOW for April 22, 2005).

Question:  What causes the crescent shape as seen here?  (select one:)

A) the Moon lies partly in the Earth's shadow.

B) We see mostly the dark side of the Moon because of the position of the Sun.

C)  The moon has rotated its dark side to face the Earth.

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an 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

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

Observers are invited to submit digital photos to: