Monday, December 9, 2013

Weirdness Around the Solstice

A little explanation of the shortest day of the year, and the earliest sunset and latest sunrise:
If you live around latitude 42N—a well-populated latitude in North America and Europe, taking in Boston, Rome, and Vladivostok—today (December 8) is the day you'll experience the earliest sunset of the year. Those who live farther north, in London or Moscow, can expect the earliest sunset on Thursday. Those farther south, in Miami or Mumbai, already had their earliest sunset a few days ago.
Wait a minute. Isn't the solstice, December 21, still more than a week away, the day of the earliest sunset? And the date of the year's latest sunrise, as well? The late sunrise and early sunset combine on the solstice to create the day with the shortest amount of daylight. Right? 
Actually, that's a fantasy. The earliest sunset really comes in the first week in December, and the latest sunrise occurs in early January. Yet December 21 really is the shortest day of the year. What sort of astronomical hijinks are responsible for this absurd state of affairs?
Blame it on Earth's non-circular orbit and its tilt in relation to the Sun.
More details if you click through the link.  This kind of stuff makes my head hurt.  It reminds me how brilliant Copernicus, Kepler and Galileo were when they were figuring out the heliocentric solar system.

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