The nights are long. You never seem to warm up. It must be winter. Or it will be anyway at 11:11 a.m. (CST) tomorrow Dec. 21 when the sun bottoms out in its yearly circuit of the sky like a cigarette crushed in an ashtray.
But every winter solstice has a silver lining; after tomorrow the sun begins moving northward again, chipping away at the darkness as it rises higher with each passing day.
Winter takes getting used to which is why we still call it fall in November and much of December. By the time the solstice rolls around on the 21st, we’ve long accepted the cold, snow and driving home at 5 with the headlights on.
The fundamental facts of life all revolve about the tilt of Earth’s axis. If our planet rotated straight up and down like Mercury, we’d have no seasons. Mid-latitudes would experience eternal spring with the sun forever stuck halfway between its summer high point and winter low. Some of you might like this … for a while.
Meanwhile, those living at the equator would see the sun directly overhead at noon every day of the year, while polar explorers and researchers would watch it skirt the horizon and never rise higher. For everyone the sun would rise and set at nearly the same time every day.
But no. The 23.5 degree tip of the Earth’s axis combined with our planet’s revolution around the sun break the monotony and create the seasons. The tilt ensures that the northern hemisphere of the planet nods toward the sun in summer and away in winter when we’re on the other end of our orbit.
As a result of that nod, the sun appears high in the sky in summer. Its longer, steeper path across the sky means longer days and more intense heat. In the winter, the northern hemisphere “leans back” from the sun. Slanted, less intense solar rays and short days follow.
On Dec. 21 the sun reaches its lowest altitude above the southern horizon at noon for the year. Here in Duluth, that’s about 20 degrees or two fists held at arm’s length. For Chicagoans, it’s 25 degrees, a bit higher. But if you live in Anchorage, the solar disk climbs to just under 6 degrees before slinking back toward the southwestern horizon.
Solstice literally means “sun stands still” and refers to the fact that around the solstice sunrise and sunset times change very little and the sun seems stuck in the same low spot in the sky. In December the sun sits at the “bottom” of its yearly path around the sky. Most of its daily motion is to the east and very little to the north. For the sun to get higher in the sky (and days to grow longer), it needs to spend more time moving “upward” or to the north. That starts happening in late January and accelerates during the spring when the sun’s path is more steeply angled to the horizon.
We’ve spent the last three months watching the sun glide to the cold bottom of the celestial sphere. Beginning tomorrow there’s nowhere to go but up. The next time you grab that snow shovel and heave a chunk of winter over the bank, know that the sun – starting tomorrow afternoon – will be on your side.