Tomorrow, Dec. 22, 2011, at 5:20 a.m. (UTC), the sun will reach its most southerly declination of -23.5 degrees. That moment will be the winter solstice, and it will come at the end of the longest night of the year.

For many, it cannot come soon enough. The ancients looked forward to the day as proof that the sun would return and another spring would soon follow. The earth would not be consumed in darkness and death.

Even modern, rational folk find relief in the solstice for a very similar reason. We have no fear of an angry god stealing the sun away from the earth, as ancient pagans once did, but the shrinking days and lengthening nights of autumn take a toll on our minds and spirits.

People have long been aware that energy flags; for some, attention and even libido decline during the winter months. It is thought that the condition is the result of low levels of serotonin or melatonin, a typical response to low levels of light. The general condition is probably rooted in our evolutionary past. Many species experience a lower metabolism in winter months due to decreased food supply. In its extreme form, some shut down altogether and go into hibernation.

In our species, the extreme form of these “winter blues” is called seasonal affective disorder, or SAD. The condition was officially named and recognized by researchers at the National Institute for Mental Health in 1984.

One of the most popular treatments for the condition is light therapy, consisting of a simple lightbox that emits far more lumens than a customary incandescent lamp. It raises the serotonin and melatonin coursing through the brain and makes a depressing day a little brighter. I have a lightbox on my desk behind my monitor, filling my eyes and face with light. I will be using it daily for at least a couple more months.

The rest of humanity may not be suffering from SAD, but the December solstice has been associated with fire and illumination since ancient times. This is due in part to the need for light and warmth, but one suspects there are deeper associations as well. The winter solstice is a time of feasting and celebration nearly everywhere in the Northern Hemisphere.

Pre-Christian Scandinavians observed the Feast of Yule and put a yule log on the hearth to honor the god Thor. Fires were lit to symbolize the return of the sun, with its light, heat, and life-giving properties.

In northern Pakistan, the Kalasha people celebrate the festival of Chaomos over seven days, including the day of the winter solstice. It involves ritual baths, singing, chanting, a torchlight procession, dancing, bonfires, and festive eating.

Jews observe Hanukkah over eight days and light the nine candles of the menorah. Hindus and Jains recognize Divali, the Festival of Lights, in late autumn. They celebrate with small oil lamps around their houses and with firecrackers and sweets.

Of course, Christians long ago adopted pagan traditions and put their own spin on them. There was a star in the East, which was transposed to the top of a Christmas tree, and that tree was decked out in all manner of bright and gaudy incandescence. The mounting of Christmas lights as art and sculpture is nothing less than surreal in modern America, as anyone who has seen the light show at James Island County Park can attest. Yet few of us are immune to the exuberance. I am not a Christian, but I have a string of lights around the front porch of my apartment.

The winter solstice gives us the opportunity to connect to our past and the earth. We should welcome both. Our past includes our pagan ancestors who deified the earth and its elements, its seasons, its natural forces. They understood the earth and belonged to it in a way that modern humankind has largely forgotten.

Whatever this season means to Christians, Jews, and those of other faiths, it should remind us all that we are of the earth. Our seasonal mood cycle, like a woman’s menstrual cycle, reminds us of who we are and how we came to be here.

Our moods and behavior, the flux and flow of our bodies, are part of the cycle of our little blue planet around the sun and the moon around our planet. This earth is our home and our sustenance. We cannot hurt it without hurting ourselves. Perhaps the discomfort we suffer in the cycles of our lives are earth’s way of reminding us of whence we came. It’s a small price to pay if we learn the lesson.

This is the season to wish one another peace on earth. Perhaps we should wish peace to the earth itself. It’s having a hard time lately.

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