Physics Photo of the Week
Earthshine on the Crescent Moon
Moon is just past new or just before new we only see a thin crescent
illuminated by the Sun. This image was taken on April 5, 2011
soon after the Sun had set below the horizon.
Of special interest is the visibility of the features on the dark side
of the Moon. This faint illumination comes from sunlight
reflected from the Earth - Earthshine. Earthshine on the Moon is
exactly analogous to Moonshine on the Earth (not an illegal
beverage...). If we were standing on the Moon facing the Earth,
we would see an almost full Earth, very bright, hence the surrounding
moonscape would also by illuminated by the Earthlight. Likewise
when we are outdoors on Earth during the full Moon, the Moon is very
bright and we can see our shadows in the Moonlight.
photo of the moon's apparent motion in the sky is shown
at right. Notice that the Moon's setting path is at an angle to
the horizontal. This angle depends on our latitude on
Earth. Compare with the recent sunrise time (PPOW
March 25, 2011). When observed from the northern
hemisphere setting objects (Sun, Moon, and stars) move down and toward
the right (north). Rising objects move up and toward the left
Photo of the
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 firstname.lastname@example.org.
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.
see the Physics Photo
the Week Archive.
Observers are invited to submit
digital photos to: