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December 21, 2002: December Solstice

Twice a year, at the March and September equinoxes, our planet Earth doesn't tilt at all in relationship to the Sun. On those two days, the Sun rises due east and sets due west the world over, and everyone on Earth receives about twelve hours of daylight followed by twelve hours of night.

Also twice a year, halfway between the equinoxes, the axis of our planet tilts to its greatest extreme. These are the solstices. At the June solstice, our Northern Hemisphere tilts TOWARD the Sun, giving us the longest day and shortest night of the year. Six months later on the flip side of the year, the December solstice finds our Northern Hemisphere tilting AWAY from the Sun - giving us the shortest day and longest night of the year.

This year, the exact moment of the winter solstice comes at 8:14 p.m. EST on December 21. At this time, the Sun is at its most southerly position, hovering directly overhead at the tropic of Capricorn. Anyplace north of the Arctic Circle now endures 24 hours of darkness, whereas anyplace south of the Antarctic Circle enjoys 24 hours of sunlight.

Everywhere outside of the Arctic and Antarctic regions, the Sun rises and sets furthest south for the year. In our Northern Hemisphere, the noonday Sun sinks to its lowest point in conjunction with the Sun rising and setting at its southernmost points.

Solstice literally means "sun still," because the Sun changes declination (south and north direction) at a snail's pace during this time of year. The Sun's change of declination in a week is less than the Sun's DAILY change of declination around equinox time.

In fact, the solstice "stand still" phenomenon is responsible for one of the season's befuddling peculiarities. At our mid-northern latitudes, the earliest sunset of the year comes two weeks BEFORE the winter solstice and the year's latest sunrise comes two weeks AFTER, even though the winter solstice is officially the shortest day of the year.

copyright 2002 by Bruce McClure

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