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Several times in my career I have attempted to explain why the shortest day of the year (the winter solstice, which is tomorrow) has neither the latest sunrise nor the earliest sunset of the year. Judging from subsequent reader questions, I haven’t had a ton of success.

Basically, it’s because the Earth goes around the sun not in a circle but an ellipse, which causes the planet to travel at different speeds at different times of the year (as Kepler first realized). That means the length of the solar-noon-to-solar-noon “day” constantly changes; it’s almost never 24 hours exactly.  We don’t factor that changes into our clocks because it would be a pain and the discrepancy isn’t obvious most of the time. This solstice/sunrise/sunset anomaly is one of the times it is obvious.

It hadn’t occurred to me, however, that different latitudes experience difference time periods between the latest sunrise and earliest sunset until I saw the excellent map shown above via this Vox article about the solstice. It comes from this brilliantly obsessive blog about climate maps put together by an Alaskan meteorologist.

It be honest, I’m a little uncertain why different latitudes alter the spread between sunrise and sunset extremes. I’ll have to think about it: 3-D visualization isn’t my strong point.

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