Monday, December 24, 2012

An unusual sunset light effect

I'm not sure if it is due to global climate change or what -- we've had snowless Christmases before -- but pretty much every bit of snow which has fallen to date this season (and it has been pretty meager) has disappeared within a day or less.

So it was that yesterday, the day before the day before Christmas, I found myself taking a cold but pleasant bicycle ride on one of my favorite routes. A significant part of it follows a river path that ends at Paradise Pond, a lovely feature of the Smith College campus.

Stopping at the overlook above the pond to catch a view of the sunset, I observed something I am pretty sure I have never seen before. The setting sun was somehow casting a vertical shaft of red, poking up from the horizon like a flaming sword. I took several photos of it, though they don't completely capture the nature of this phenomenon.

Here's a zoomed-in view of the strange light…

… and here's a panoramic view showing the setting.

I wonder what trick of physics created this intriguing light effect? -- PL

1 comment:

Mark H said...

Hey Pete,
Wow, that is pretty cool. I have never seen a sunset like that. I missed it in all the hustle and bustle of Christmas Eve. I noticed a couple of neat atmospheric effects yesterday. I woke up at four in the morning and stepped outside at about 4:30Am. When I looked at the sky it was very clear and, I noticed a very bright light on the horizon. The light was flashing red, blue, and green. At first I thought it was an airplane. After observing it for about 30 seconds I noticed it did not move at all so, it could not be a plane. I figured it was a star, most likely Sirius, the brightest star in the night sky. I have observed Sirius many times in the past but, never have I seen it put on a little multicolored lightshow. I was curios as to what caused this “light show” effect so I went inside and researched it. From what I gather stars appear to twinkle because of disturbances in the earth’s atmosphere. The lower the star is in the sky, the more atmosphere you are looking through so the star may appear to twinkle more and change colors. I was viewing Sirius just above the horizon so; I am guessing that is the explanation for what I witnessed. It was a beautiful sight to behold. A half hour later at 5AM I could still see Sirius, it is one of the last stars to fade away at dawn, but it was no longer doing its light show.
Last night when we came home from Christmas Eve with my parents my wife pointed out the halo around the moon. Moon halos caused by tiny ice crystals that have gathered twenty thousand feet above the ground, as thin, wispy clouds. These clouds are so thin, you might not notice them at night, if it weren't for their effect on the moonlight. Incoming light rays from the moon are bent, or diffracted, by these ice crystals at an angle of 22 degrees. This means that in addition to the direct moonlight, you will also see diffracted moonlight in a circle 22 degrees away from the moon. It is a very neat effect.
There where lots of very beautiful atmospheric effects going on yesterday. I’m happy I was able to observe a couple of them. I missed the sunset but, I’m fortunate someone took some pictures to share.
I’m pleased to see that you have survived the “End of the World”! Hope you and yours have a very Merry Christmas!
Thanks for sharing,