At 12:47 Eastern Time or 17:47* Z time, formerly Greenwich Mean Time, the earth reached its furthest tilt away from the sun, which rises only to the Tropic of Capricorn. As everyone knows, the earth’s axis of rotation is tilted away from the plane of its revolution around the sun by about 23.27 degrees. On the winter solstice, the that axis is pointed directly away from the sun. The north polar regions are in darkness and get very cold, spilling their cold air down over Canada, Scandinavia, and Russia. At the same time, the earth is relatively close to the sun, showing that spreading the sunlight over a large area has much more effect than a small change in distance. The southern polar regions get almost continuous daylight and the tropics have their summer, made even hotter by closeness to the sun.
In spring and fall, the sun shines towards the sides of the axis and sunlight falls evenly on north and south. In the summer, the earth’s axis tilts towards the sun. The North has its summer and long days, while the South has its winter and short days, made even cooler by distance from the sun.
In Northern Europe, the short, cold days and long, depressing nights, so soon after the late harvest and autumn slaughter of animals for winter food, made a cheering feast when the sun began to rise higher in the sky and the days began to lengthen. This festival has come down to us as Yule.
*Correction: 17:47, not 16:47. I can never get that “Spring forward, Fall back” rule reliably correct.
P.S. See “Keep Han in Hanukkah.”