Tropic of Capricorn
Our Sun reached its farthest southern point, the Tropic of Capricorn, at 4:32 a.m. PST on December 21 this year and has since begun its six-month swing back into our northern sky. We know that the coldest part of winter is still ahead of us, but from experience we also have hopes that the Sun is beginning to end its hibernation. This tropic has little to do with sun and warmth.Tropic comes from the Greek word tropos meaning turning. The Sun turns north if it’s at the Tropic of Capricorn, or south if it’s at the Tropic of Cancer in its yearly sashay between these two points. Thus the Tropic of Capricorn is the imaginary line traced by the Sun as it circles the Earth east to west at 23 ½º South. This is the latitude at which the Sun is directly overhead at noon in the southern hemisphere on the shortest day of the year for us in the north. This latitude is as far south as the Sun ever moves; from here it turns north until it reaches the opposite Tropic of Cancer in June. The area between these two Tropics has no significant temperature variation over the year because the Sun is always overhead. From this comes the reason it is “tropically” sultry. We on Bainbridge experience the changing seasons caused by the Earth’s tilt because we’re well north of both Tropics.
The moment that the Sun reaches 23 ½º S is called the winter solstice—the time in December when the Sun appears to stand still. Years ago this was when people wondered if spring would ever come, or if they were doomed to eternal darkness and cold. The apparent movement of the Sun in relation to the stars over the seasons is due to Earth’s tilt of 23 ½º in its axis of rotation around the Sun. This tilt, plus the effects of the pull of gravity on the Earth from the Sun and the Moon and its daily revolution cause it to wobble slowly (every 26,000 years) and smoothly in its orientation to the stars, a bit like the wobbling of a top.(But the Earth doesn’t fall down like a top does.) This wobble is called the precession of the equinoxes.
And Capricorn? Likewise it now has little to do with marking the season. It’s the constellation known as “The Goat,” the tenth sign of the astrological zodiac. In the 2nd century BC the astronomer Hipparchus observed that the apparent position of the Sun at the winter solstice was in this constellation. He identified it as such, and the name has stuck ever since. The Earth, however, has not stayed stuck; it’s precessed, so that now the Sun is in a different constellation, that of Gemini, on December 21. In another two thousand years the solstice will have continued to disregard astrologers and have moved on to Taurus. For the Romans in the time of the Caesars, the winter solstice was the Saturnalia holiday. It originally was a one-day—December 17—event honoring Saturn as the god of sowing. Then it expanded into a week’s festivities culminating in the festival of Sol Invictus (the Unconquered Sun) on December 25. They exchanged gifts during this week, wished everyone peace and prosperity, plowed the ground, and sowed their seeds.
December was the tenth and last month of the Roman calendar. Romans drew a parallel between the birth of a baby in the tenth month after its nine-month gestation, and the hope that the Sun would waken from its snowy hibernation and create new life during this December celebration.