The day with the least sunshine, the winter solstice is here. Thursday, December 21, will be the shortest day of 2017 for anyone living north of the equator. Brian Resnick and Brad Plumer at Vox point out that if pagan rituals are your thing, this is probably a big moment for you.

If you are not a druid, the official first day of winter is notable for other reasons. The authors explain that the winter solstice occurs when the sun is directly over the Tropic of Capricorn or 23.5° south latitude. This will occur at exactly 11:28 am Eastern time on December 21, 2017.

Most people know why we have a winter solstice, but for the flat-worlders – the Earth orbits around the sun on a tilted axis (likely because our planet collided with some other massive object billions of years ago, back when it was still being formed).

So between September and March, Earth’s Northern Hemisphere gets less exposure to direct sunlight over the course of a day. The rest of the year, the north gets more direct sunlight and the Southern Hemisphere gets less. It’s the reason for the seasons.

How much sunlight you get on the winter solstice, depends on where 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.

If you live near the Arctic Circle, like my friend Mari, you’ll barely get any daylight during the solstice. Fairbanks, Alaska, for instance, will get three hours and 41 minutes. (If you live north of the circle, you’ll get none at all.)

For me, the reason the winter solstice is most notable, it marks the official first day of winter and the arrival of the coldest days of the year — usually in January or February, depending on where you live.

There’s a delay between when there’s the least sun and when the air temperatures are actually coldest. A big reason for this “seasonal lag” is that the Earth’s massive oceans absorb much of the sun’s energy and release it slowly, over time. The same thing happens in summer — there’s a delay between when solar insolation is at its most (the summer solstice in June) and when the hottest months are (usually July or August).

Today the solstices largely pass without much hoopla. But 5,000 years ago it meant a great deal to the druid and pagan inhabitants of the British Isles. The early Brits built Stonehenge which experts say marked ancient solstices and equinoxes. That’s because the structure is directly aligned toward the sunset during the winter solstice. (The sun also rises directly over the Heel Stone during the summer solstice.)

Teresa Wilson of the American Astronomical Society told the authors:

While the summer solstice draws a larger crowd, the winter solstice may have been more important to the ancient builders. At this time, cattle were slaughtered so the animals did not need to be fed through the winter, and wine and beer made previously had finally fermented.

Even today, humans still gather to pay homage to the winter solstice at Stonehenge.

rb-

At least the winter solstice at Stonehenge looks like a pretty good party. If you like sleeping in, it can arguably be one of the most exciting days of the winter. No annoying sun bothering you in the morning.

Related article

• Stonehenge winter solstice celebrated by a crowd of thousands (BBC)

Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.