with a photo of the sunrise on the spring equinox! On the spring
equinox the Sun rises due east on the celestial equator and sets due
west. The length of the night is equal to the length of the day,
hence the name "equinox".
Only 3 months ago in late December the Sun appeared to be located the
furthest south as it gets throughout the year. This date near
Dec. 20-22 is called the "winter solstice". Notice how much
further to the right (south in the photo below) the Sun rose on the
winter solstice than
it does on the equinox. The date
of the photo is not exactly on the winter solstice, but constraints of
weather prevented photographing the sunrise on the exact date.
These two pictures are reproduced on the same scale.
Beginning on last fall's equinox (Sept. 22, 2007) and the spring
equinox (Mar. 20, 2008) I obtained photographs of the rising Sun
roughly once a week so we can see the "motion" of the sunrise point
throughout the fall-winter seasons. These photos are played in an
animated sequence below. Notice the great variety in the weather
revealed in the images of the clouds at sunrise throughout the two
seasons. Each frame of the animation sequence had to be aligned
because the camera was hand-held. Astronomy image processing
software was used to align each digital image. The word
"solstice" literally means the "Sun stands still". As you notice
on the animation, the Sun briefly "stops" its north-south "motion" as
it reverses direction and the longer days return.
Photo of the
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 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.