December 22 – the Shortest Day of 2011

The shortest day of 2011 will be Thursday, December 22. The winter solstice will occur at 12:30 a.m. EST (05:30 GMT), when the sun will be passing over the Tropic of Capricorn. Solstice is a staying of the sun‘s apparent motion over the latitudes of the Earth. During summer solstice, the sun stops its northward motion and begins heading south. While during winter solstice, it turns north. Sun crosses the equator at the vernal equinox, passing into the Northern Hemisphere on March 20, at 1:14 a.m. EDT (or on March 19 for those living in the Mountain and Pacific Time Zones). Every year on June 20, the altitude of the midday sun is lowering and its direct rays are migrating to the south.

On those summer days, the sun‘s altitude above the horizon at noontime is 47 degrees higher than it is now. From ancient times people were following the motion of the sun. At that time people were thinking that the sun machinery might break down someday, and the sun would continue southward, never to return. The lowering of the sun was causing fear and wonder.  When the ancients saw the sun stop and slowly climb to a higher midday location, they were expecting the spring is getting back. Many cultures of the world had sun solstice celebrations. In Persia, the solstice marked the birthday of Mithra, the Sun King. In ancient times, Dec. 25 was the date of the great Roman festival of Saturnalia, which celebrated around the time of the winter sun solstice. And in 275 A.D., the Roman Emperor, Aurelian, commemorated a feast day coinciding with the winter solstice: Die Natalis Invicti Solis (“The Birthday of the Unconquered Sun“).
source: www.space.com