Though the least total daylight is on the solstice, the earlying of sunset and latening of sunrise are NOT SYMMETRICAL.
This is due to factors I struggle and fail to understand every year— the angle of the ecliptic, the elliptical shape of the earth's orbit, the shape of the analemma (that mysterious figure that the sun draws on the sky in the course of a year), a still more mysterious explanatory factor called the equation of time, and so on—
I am happy to report that here the earliest sunset is December 6. Then it doesn't change through the 14th, but gets no worse. Same time each day. Then it starts getting marginally later. The early darkness will begin to improve in a few more days; it's nearly over.
This year, however, we add to the annual failure to hold all these visualization factors in mind, the news that the date of the earliest sunset varies by latitude. The fact that the earliest sunset near the equator falls in November kicks my brain out of gear.
P.S. Analemma photo: sun taken at the same time of day, once a week for a year, on a single piece of film. Other people have done it since, but when a Sky&Telescope editor named Dennis DiCiccio did it in 1978 it had never been done before. Plus he had to do it for TWO years, because the first year he aimed the camera wrong and part of the figure was off the film :-( Everyone who does such a photo now always mentions DiCiccio—it's that science history, standing-on-the-shoulders-of-giants stuff.
1 comment:
Ha, ha...not symmetrical. Have you ever looked at a closeup photo of a human being by blocking out one side of the face at a time and then comparing what you see? The human face is not symmetrical either. It's a very fascinating experiment. You see different "sides" of the same person right there staring back at you from the photo. I've been doing this for years as an amusement. Sometimes it's quite revealing. Only something that is fabricated is symmetrical. Nature is not. Or at least I have not found anything in nature that is.
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