dipper@utastro.UUCP (Debbie Byrd) (12/21/85)
Today marks the December solstice -- when days stop getting shorter and start lengthening again. More -- after this. December 21: The December Solstice If you've been watching the western horizon at sunset, you've seen the sun go down a little farther to the south each evening. But that southward trek ends this evening -- because today is the December solstice -- which marks the shortest day of the year for the northern hemisphere. A solstice occurs every year at this time as our world moves around the sun. This is a special day because Earth tilts on its axis with respect to the plane of our orbit. Every year at this time, Earth's south pole points as much as it can toward the sun. At the south pole around now, the sun never sets at all -- and in the southern hemisphere, people are enjoying long, leisurely days of summer -- and no doubt celebrations of the summer solstice. For us, this solstice marks the beginning of winter -- and the shortest day of the year. There are fewer total seconds of daylight today -- although, for latitudes in the United States, it may SEEM as though the days started getting longer a few weeks ago. That's because the earliest sunset always preceeds the shortest day by some days or weeks, depending on your latitude. For our latitude in Austin, the sun is setting later now than it was on December 1. But the sun is rising later now as well -- giving us an overall shorter day. After today, the overall day will start getting longer -- but the latest sunrises are still to come, in early January. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin