The Winter Solstice

Date: December 22
Time: 5:15 pm, sunset
Place: the western sky

A celestial event known as the Winter Solstice will occur on December 22nd. You’ll hear about it from your favorite weather person, but typically with an abbreviated (and sometimes incorrect) explanation.

The path the Sun appears to take through the sky shifts slowly from season to season. This shift causes the sunset and sunrise points to move north and south along the horizon. We all learned early on how “the Sun rises in the east and sets in the west,” but this is only approximately true. West is 270° on the compass, but the Sun only sets there on the Spring and Fall Equinoxes. At other times it sets north or south of true west. Same with sunrise in the east.

How much north or south depends on the date and also on your latitude. But wherever you are*, the Winter Solstice marks the extreme southern excursion of this sunset point. In Arizona, or anywhere else near latitude 34° N, that point is at compass heading 241°, a direction better described as WSW (west by southwest). This is also the shortest day of the year, with only 9 hr 45 min of daylight.

December 23rd will see the Sun set (and rise) farther north, moving higher through the sky. Days will lengthen, average temperatures will increase, and Summer, as always, will arrive exactly on schedule.

*Things get a little more complicated near the poles, but that’s a topic for another column.

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