Solstice turns out to be real


I started the day convinced that the Winter Solstice was merely a myth invented by pagans and picked up by atheists in an attempt to make themselves feel better during the darkest days of the year. A crutch to give them something to celebrate in the face of overwhelming hopelessness.

The source of this conviction was the data I have been collecting regarding sunrise out my kitchen window. The data is plotted on the left. As you can clearly see sunrise is continuing to get later and later well past the alleged "winter solstice" of 12/21.

My position now, later in the day, is that the winter solstice is, in fact, a real event, but much more complicated than a simple pagan could possibly comprehend (not withstanding Stongehenge). Or perhaps more than I can possibly comprehend. All the tools online agree that the 12/21 is the shortest day in the year, and they also agree with the data that I have collected which indicates that although 12/21 is the shortest day of the year, sunrise will continue to get later until sometime in mid-January. It's just that sunset stopped getting earlier on 12/21 and started to get later faster than sunrise was getting later. (It's kind of like a payment-option mortgage back in the good times)

So right now I don't quite understand why the sunrise and sunset don't increase and decrease symmetrically. Why doesn't the sunrise get earlier when the sunset gets later? Is it because I'm not in the middle of the timezone? Lazy internet, wikipedia has failed me, what do you say?

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Irvine, CA-specific data from corroborates the traditional story. Posted at . How, exactly, doesn't it mesh with your data? Also, methods?

Running hypothesis: you perceive light differently, pre-morning coffee.

Posted by: Sam at December 30, 2008 12:09 AM

Just realized/was shocked that this means you wake up before sunrise.

Posted by: Sam at December 30, 2008 12:16 AM

I do wake up before sunrise (gasp!)

And I think that table does mesh with my data. My sunrise times won't be the same because I don't have a clean horizon. I'm timing the sunrise over Bonita Canyon. The trend, though, is consistent. Coffee notwithstanding.

In your data the sunrise continues to get later even after 12/21. Same with my data. Before this experiment I would have thought that on 12/21 the sunrise would start getting earlier and sunset later. That isn't the case in my data, or the data that you posted.

Posted by: Don at December 30, 2008 10:26 AM

From a private response from an Astronomy Professor at UCI Irvine:

"I can give you a shortish answer and maybe explain it better the next time we run into each other. It has to do with the fact that clocks are set using mean solar time (the time it would be if the earth's axis wasn't tilted with respect to its orbit around the sun, and if the orbit were perfectly circular).
     The 23.5 degree tilt and the fact that the orbit isn't quite circular both work to make local high-noon later than a clock's noon in the early winter. This shifts both sunrise and sunset later relative to the clock (note that without this effect, sunrise will become later and sunset will become earlier, as you might originally think). This systematic shift in both sunrise and sunset messes up your expectation that they should expand uniformly around clock noon.
     Why does this happen? Before solstice the sun is moving slightly slower to the east than it would if the earth weren't tilted. After solstice, it goes the other way.

So I read this as: the earths orbit is not round and clocks assume that it is.

Posted by: Don at December 31, 2008 12:14 PM

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