As we enter the darkest time of the year many of us, especially this year, find it depressing and no cause for celebration. While seasonal affective disorder (SAD) may afflict up to 3 million Americans each year even those of us fortunate enough to not endure this may still feel a little blue. Conversely, personally I find that the winter solstice is reason to celebrate: the Sun is coming back! This year the solstice occurs on December 21 (it varies year to year) and here in Bucks County we will have only 9 hours and 18 minutes of daylight. By the time December 22 rolls around we’ll have one additional minute and by New Year’s Day we’ll have 5 more minutes. Then things really start to accelerate and by February 3 we’ll have a full hour more of daylight than we did on the solstice!
So, what causes these seasonal shifts in day length? Although the Earth’s orbit is not a perfect circle, it is not because we are farther from the sun in the winter. It has to do with the fact that the Earth’s axis is tilted relative to our orbit around the sun.
As we make our circuit around the sun, the portion of the Earth that is directed at our star varies such that on what we call the winter solstice the southern hemisphere is facing the sun, while the northern hemisphere is pointed diagonally away.
This astronomical event has had great cultural significance throughout history and prehistory. The great stone circles of Stonehenge, Avebury and The Ring of Brodgar in the British Isles, the Carlsbrook stone arrangement in Australia and Altit Yam in Israel are thought to have been built to align with the sunset on the solstice, possibly signifying the return of the sun. Anthropologists have considered that some of our most beloved winter traditions have their origins in our ancestral celebrations of the lengthening of daylight.
Whatever its origin, we hope your solstice-adjacent celebration is a happy one!