The Inconstant Sun
We live by grace of the sun. All of life on Earth is the gift of the sun.
It is no secret. Human beings knew it long before they had developed what we call civilization. In north temperate latitudes, the sun was watched anxiously, not merely for the sunrise that would yield light and at least a measure of warmth at the end of the long, cold, dark night, but also during the months of its decline, which marked the inevitable coming of winter.
Through all the summer and fall, through all the days of dwindling warmth and increasing chill, the noonday sun attained each day a lower height in the southern sky than the day before. It gave less heat each day, and there had to be the fear that, though it had not happened in previous years, in this year the sun would sink indefinitely, disappear beyond the southern horizon, and leave the world to darkness, cold, and death.
It never happened. The sun sank at a steadily lower rate and the day came when it reached the lowest spot past which it would not sink. We call that the "winter solstice" ("standstill of the sun"). It falls on the day we now call December 21, and though the bitter winter lay ahead, the noonday sun was climbing higher and higher and the promise of eventual spring and rebirth was sure.
The rise should not continue indefinitely either, for otherwise there would be increasing heat and drought until life became impossible. Always, however, there was an upper limit, too, to the sun's position, the "summer solstice," which we now mark as falling on June 21.
Ancient peoples the world over, long before they had writing or any but the simplest technology, worked out ways of keeping track of the shifting sun. Stonehenge, in southwestern England, that circle of enormous rocks, is