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Physics Photo of the Week

September 9, 2005

Moon Photos by Astronomy class

The astronomy class at Warren Wilson College made photographs of the moon through a telescope on Thursday, September 8, 2005, when the moon was a crescent phase.  This is Molly Sternberg's image. The moon phase was about 5 days after the new moon.  The moon was seen in the southwestern sky soon after sunset.  The sun was below the horizon to the lower right in the photo.  The reason the moon is crescent shaped is NOT due to the earth's shadow, but because of the angle between the sun, moon, and earth.  Most of the moon's surface on the side facing the earth is on the "night" side of the moon.  The moon is in its own shadow, not the earth's shadow!

On Molly's photo above notice the details of the craters near the terminator - the boundary between the sunlit part of the moon and the darkness.  That is because the craters and mountains cast long shadows on the moonscape.

The image at left, made by Bo Collins, zooms in on the crater Theopilus.  Notice the central peak in this crater.  The central peak in this crater and in many other craters on the moon is caused by the rebound effect when the crater was created millions of years ago by a catastrophic impact from a comet or small asteroid.  Cosmic impacts melt the material of the planet or satellite due to the enormous kinetic energy of the impacting body.  The material of the moon rebounded immediately after the impact and formed the peak.  This is similar to the rebound splash when a stone is thrown into a pond.

The reddish color of these photos is due to the moon's position low in the sky.  The moonlight travels through a larger thickness of haze which "reddens" the moon - similar to the red sun at sunset.

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 all Physics Photo of the Week for 2005