Jimmy Westlake: Winter solstice
December 22, 2009
Steamboat Springs — The winter solstice, marking the moment autumn ends and winter begins in the northern hemisphere, occurred Monday night at 10:47 p.m. The winter solstice is always a very happy day and a very SAD day. Here's why:
If the Earth sat upright on its rotational axis, the sun would simply hover over the Earth's equator all year long and we would not experience any seasonal changes. Instead, the 23.5-degree tilt of the Earth on its axis causes the sun to wander 23.5 degrees north of the equator and 23.5 degrees south of the equator. The dates of the two extremes are called the solstices. Solstice is a word that literally means "the sun stands still."
You see, the farther south the sun moves, the fewer hours of sunlight we enjoy each day in the northern hemisphere. As we approach the date of the winter solstice, our days become shorter and shorter as the sun heads south. If it kept going, we eventually would be cast into eternal night.
It is a happy day, indeed, when the sun bottoms out and begins to head north again. The ancient civilizations broke into wild celebration when the sun stopped heading south and "stood still" for a day. The Romans used to pull out all of the plugs and throw a huge party called Saturnalia. They celebrated the "birthday of the invincible sun." With each successive day after the winter solstice, the daylight hours grow longer and the promise of spring was in the frosty air.
Unfortunately, the news is not all good for folks who suffer from SAD, or seasonal affective disorder. The waning sunlight can cause some people to sink into the deep depression of SAD. For the two winters that I lived in Anchorage, Alaska, I felt the sting of SAD a little bit myself when the sun came up at 11 a.m. and set only four hours later at 3 p.m. The therapy for SAD is to sit for extended periods of time under bright artificial lighting. This seems to satisfy the body's need for sunlight and can pull SAD sufferers out of their deep, dark hole.
Evergreen trees have become a part of our seasonal celebrations because they symbolize the triumph of life over the cold and dark of winter. During these first few dark and dreary days of winter, it might help to remember that while we look forward to three months of winter, folks down under are doing just the opposite — looking forward to three months of summer.
Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published around the world. Check out Jimmy's Web site at http://www.jwestlake.com.