By Rod Hill on 2011-12-20
Winter Solstice 2011
Winter officially begins on Wednesday, December 21 at 9:30 p.m. in the Pacific Time Zone. At that moment the sun, in the constellation of Sagittarius, sits over the Tropic of Capricorn at latitude of 23.5 degrees south. This date is the Winter Solstice, the day on which the Earth's northern pole is tipped away from the sun.
As seen from Portland, the sun will reach its lowest southern point in the sky at 21 & ½ degrees on the horizon. Because of the low angle of the sun's arc, it will produce the longest and most spectacular sunrises and sunsets of the year. On December 18-21, we will have nearly 8.5 hours of daylight to enjoy.
On the day of the winter solstice, the sun will be directly over the Tropic of Capricorn at noon and at the same time, the region above the Arctic Circle will be in total darkness for 24 hours! Incidentally, the Tropic of Capricorn is so named because a few thousand years ago the sun resided among the stars of the constellation Capricornus on the solstice date. The word solstice is derived from the Latin sol-stitium, for sun-standing. The winter solstice is the time of the year when the sun stops its southern climb and stands briefly before turning back toward the equator.
On the winter solstice the Sun from our Earth perspective appears to stand still. This was of great concern to our ancestors because they believed that all heavenly objects were gods and that if the Sun god was displeased, it might just continue to keep rising and setting farther south until it eventually disappeared. The day of the winter solstice was met with great anticipation, a bit of anxiety and a lot of celebration. Right after the solstice the Sun invariably started rising and setting a little bit farther north each day. Our ancestors interpreted the sun's rising to mean that the world would not be plunged into eternal winter and that spring would once again eventually come.
It is easy to see why our ancestors could be frightened by the sun's movements. They believed that if the Sun continued its journey south, the world would be plunged into eternal night. In fact, winter solstice celebrations were so widespread in our western culture that the early Christian church decided to move Christmas to the time of the solstice. For those of you who dislike the dark winter days, look at the bright side: after December 21, the days will gradually grow longer and the night shorter as Earth completes its yearly journey around the sun.
___________________________________________
The above is courtesy of Mr. Jim Todd, OMSI Planetarium Manager
Early Saturday Sky Show