Physics Photo of the Week
November 30, 2012
Belt of Venus
Soon after sunset when the skies are
exceptionally clear and cloudless, we can see the shadow of
the Earth in the east - opposite the sunset. The dark
sky close to the horizon is the part of the Earth's
atmosphere in the distance that is already night. The
so-called "Belt of Venus" is the "warm" reddish glow just
above the
earth's shadow but beneath the blue sky at higher
elevations. The warm glow is the result of
back-scattered sunlight from the air molecules in a
direction almost opposite the direction of sunlight.
At higher elevations, the region of the blue sky, the
sunlight direction of scatter is such that only the blue
colors are scattered toward the observer. In the
"belt" region, all wavelengths that reach the distant air
are scattered. In the shadow area there is virtually
no light to scatter back to the observer. Click on the
image above to see a higher-resolution image. The
image was taken on Wednesday, November 28, 2012.
Another photo of the "anti-sunset" and the Belt of Venus
(including a sequence) was posted on Physics
Photo of the Week for January 21, 2005)
The structure in the foreground is the
partially-completed College View Observatory. The roof
(framework only at this stage) is built to roll-off the
structure to open up the sky for an astronomical telescope
to be installed upon completion. The image at the
right
shows a close-up of one of the roof casters. Click here
on the image for a video of the first test rolling of the
roof - about one inch of easy movement!
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 dcollins@warren-wilson.edu.
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.
