Jimmy Westlake: Sun bottoms out this week
December 17, 2013
Steamboat Springs — The winter solstice is the astronomical moment that marks the end of the season of fall and the beginning of winter in the Northern Hemisphere. It happens this year at 10:11 a.m. MST Saturday. The winter solstice is a very happy day and a very sad day … literally SAD. Here's why.
If the Earth sat upright on its rotational axis, then the sun simply would 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 during the year. The dates of the two extremes are our solstices, from a word that literally means, "the sun stands still."
The farther south the sun moves, the fewer hours of sunlight we enjoy each day — so as we approach the date of the winter solstice, our daylight hours dwindle 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 move 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 is in the frosty air.
Unfortunately, the news is not all good for some 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 10 a.m. and set only five hours later at 3 p.m. in the dead of winter. Fortunately, as an astronomer, I had plenty to do to fill the long Alaska nights. 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 help pull SAD sufferers out of their deep, dark hole.
Evergreen trees have become part of our seasonal celebrations because they symbolize the triumph of life versus the cold and dark of winter. During these last few dark and dreary days near the solstice, 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 hot fun in the summer sun.
Happy winter solstice!
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His Celestial News column appears weekly in the Steamboat Today newspaper, and his Cosmic Moment radio spots can be heard on local radio station KFMU. Check out "Jimmy's 2014 Cosmic Calendar" of sky events on his website at http://www.jwestlake.com. It features 12 of his best astrophotographs and a day-by-day listing of cool celestial events that you and your family can enjoy watching in 2014. Proceeds from the sale of Cosmic Calendars help to support the CMC SKY Club.
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