This Saturday marks the annual winter solstice, the darkest night of the year for anyone living in the northern hemisphere. It's a major focus of pagan celebrations and marks the first official day of winter.
The solstice actually occurs when the sun is directly over the Tropic of Capricorn, or 23.5° south latitude. This year, it will occur at 11:19 pm Eastern time on Saturday.
So what's the big deal?
1) Here's why we have solstices.
The reason we have seasons, solstices, and the changing length of daylight hours is due to the fact that Earth spins on a tilted axis.
The tilt means that for half the year, the earth is tilted towards the north pole and for the other half it's tilted towards the south. It shifts which side of the planet that gets exposure to the sun.
In the Northern Hemisphere, “peak” sunlight usually occurs on June 20, 21 or 22 of any given year. That’s the summer solstice. By contrast, the Southern Hemisphere reaches peak sunlight on December 21, 22 or 23 and the north hits peak darkness — that’s our winter solstice.
2) Is the solstice actually the first day of winter?
Just because it's the shortest day of the year and typically smack dab in the middle of when the cold season, does that mean it's supposed to be the coldest?
Well, that depends on whether or not you measure the seasons by the place Earth has in the galaxy or whether you measure it based on how cold things get.
The solstice is more of an astronomy thing than a weather thing. Whether or not it's the actual coldest day of the year remains to be seen.
3) How many hours of sunlight will I get on the solstice?
Depends. Where do you live?
The farther north from the equator you are, the less sunlight you’ll get during the solstice — and the longer the night will be. Alaska climatologist Brian Brettschneider created this terrific guide for the United States:
You can check out how much light you’ll get on the solstice on TimeAndDate.com.
4) Is the winter solstice the coldest day of the year?
Naaaaah. I mean, not usually. Anyone who lives in a snowy state will tell you it's usually January or February.
Maybe it should be, but there's this thing called seasonal lag which makes the ocean capture most of the sun's energy and release it slowly over of time.
5) Pagans, Stonehenge, and Winter Rites.
To many pagan cultures, winter was the season of death. It was a time when the world was cold, where creatures went into hiding, and when the fields weren't yielding any new foods. Early cultures would slaughter full sized animals so they wouldn't have to feed them, and the beer had finished fermenting. These events had achieved religious significance over time.
No one really know why Stonehenge was built, but the theory goes that it was used to measure solstices and equinoxes.
7) Are there solstices on other planets?
Hell yeah there are!
Every planet in our solar system rotates on a tilted access, so they all have seasonal solstices. The question is how pronounced each planet's tilt is. Some of these tilts are minor (like Mercury, which is tilted at 2.11 degrees). But others are more like the Earth (23.5 degrees) or are even more extreme (Uranus is tilted 98 degrees!)
So there ya go. You can celebrate the solstice the old fashioned way, by getting drunk, slaughtering a goat, and singing mournful songs to forgotten gods. Or you can just do what I do: stay at home and watch Home Alone for the billionth time.