NERDING OUT
BY JENNY BROWN
ON DECEMBER 21, go outside at noon and look at your shadow: It’s the longest one you’ll cast at that time all year. That’s because the sun, which has been gradually descending in the sky since the start of summer, will trace its lowest arc—signaling the winter solstice and, with it, the first day of the season. Let’s learn some more.
The word “solstice” comes from the Latin solstitium, or “sun standing still,” since the sun seems to follow the same path for several days. Its arc does change, but only a bit. We’ll gain mere seconds of light in the days after the 21st, with the pace increasing to minutes as the season progresses.
Of course, as Copernicus taught us, the sun isn’t really moving around in the sky. Solstices occur because of the earth’s journey through space— specifically, its orbit around the sun at a 23.5° tilt. When its top half leans farthest from the sun (between December 20 and 23 every year), the northern hemisphere gets the least amount of light. At the same time (and yes, solstices come at a particular time—this year, the winter one is at 10:27 p.m. ET), the southern hemisphere points most directly at the sun and has its summer solstice. The spring and fall equinoxes (from the Latin for “equal night”) occur when the whole planet receives roughly 12 hours each of light and darkness.
Stonehenge gets all the attention, but prehistoric structures that align with the sun on the solstices exist around the world, including in Peru, Ireland, Jordan, Egypt, and even the U.S. In Illinois, archaeologists have reconstructed what’s known as “Cahokia Woodhenge,” a circle of cedar posts originally built by Indigenous people 1,000 years ago.
For millennia, the winter solstice has been an occasion for eating and celebration. Ancient people—they’re just like us!—were grateful for the return of sunlight and started traditions that persist today. At the Iranian Yalda festival, dating back to Babylonian times, pomegranates and watermelon symbolize the rising sun. In East Asia, the 2,000-year-old Dongzhi festival involves honoring family and heaven. Yule was a 12-day pagan Norse festival later replaced by Christmas, though some customs (like burning a Yule log) remain—as, of course, does the name itself.