Physics Photo of the Week

Warren Wilson College

January 21, 2005

Anti-sunset and Moonrise

On November 26, 2004, I had the excellent opportunity to photograph the sky and mountainous horizon to the east of Warren Wilson College on a "crystal-clear" evening as the sun was setting.  The sun is just setting in the west behind the camera.  Notice that the shadow caused by the horizon behind the camera lies just at the base of the Four Brothers mountain.  The light areas in the foreground are the wildlife pond in the WWC farm pasture (right) and a wet spot in the field (left) that hasn't dried up since the September, 2004 floods.

The sequence of photos shows the successive images of the sky as the sun continues to set - the shadow rises higher on the mountain until the earth's shadow veers out into the atmosphere beyond the landforms.  In the last picture, the mountain is completely in earth's shadow, and the dark sky near the horizon is the earth's shadow actually penetrating the atmosphere behond the horizon.  The land features in the foreground are a little more visible than in the first photo because the camera exposure setting was changed due to the overall decrease in light. 

As the sequence progresses, the shadow of the earth rises higher in the sky as the sun dips lower below the horizon behind the camera.  On this night, the moon is opposite the earth from the sun and will soon make its appearance rising from behind the Four Brothers.

Quiz Question:  What is the apparent shape of the moon seen by the observer when the moon finally rises?

A.  The full disk of the moon is seen because the moon is opposite the sun from the earth..
B.  A crescent shape of the moon is seen because it is rising soon after sunset.

C.  A partial "disk of the moon is seen because the moon lies partially in the earth's shadow.

Only after you have made your selection, should you click here to view the moon and to play an animated sequence.  The animated file is quite large, so please have patience.