time reversal

the stories of four physicists separated by the whims of fate

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Sun Dogs and snowballs

December 22nd, 2008 by liz

The sun here is very very bright, and it never goes down in the summer. It gets overcast here, but it never really precipitates. Sometimes, the sky fills with tiny ice crystals that burn to breathe in. Luckily, these ice crystals have a good side–they create a phenomena called “Sun Dogs.” Basically, the ice crystals reflect and refract light from the sun, and some cool effects occur. The most noticeable of these effects are two bright spots with a bit of rainbow coloring on either side of the sun, and a “false sunrise,” which is basically just a really bright spot on the horizon. We happen to see the false sunrise at the South Pole because the sun is at the right elevation in the sky. On good days there is a rainbow ring all the way around the sun intersecting the bright spots, and on really good days you get a partial secondary ring outside of the first ring with the rainbow colors reversed. It’s amazing.

The only real problem is that you end up staring at the sun a lot when the ice crystals are up because the Sun Dogs are so cool. Here’s an attempt at a photo of the sun dogs I saw a few days ago. You can see the two side lobes and the primary ring. I used my hand to block out the sun so the camera CCD wouldn’t saturate. Later that day there was an awesome full ring in bright rainbow colors and a partial secondary ring, but I don’t have a wide angle lens so I couldn’t photograph it.

Sun Dogs at the south pole

If you want to learn more about how rainbows and other refractive phenomena work, see Walter Lewin’s Rainbow Lecture.

In other news, my advisor (Bill) arrived at the Pole a few days ago. Me and another grad student (Abby) got to DSL a few minutes before Bill did, so we collected a bunch of snowballs and staged an ambush from the balcony. Unfortunately, Bill was not deterred by our barrage of snowballs, and he picked up a huge chunk (20 lbs.) of snow and threw it at us. Also rather unfortunately, it hit me in the head and I crumpled to the ground in a heap. I looked up and there were two blurry versions of Bill asking me if I was alright. Never fear, I’m completely fine, but I never thought I would almost get knocked out by my professor. Did you know that horseplay is banned at the South Pole?

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