Winter solstice is here (in the northern hemisphere, anyway; if you live south of the equator, this isn’t the article for you)! The shortest day of the year (and the longest night) will come and go today, and from now on, the days will be getting longer (at least until summer, when the process starts all over again).
Here are some quick facts you need to know about the unofficial holiday.
What’s Stonehenge (The Feature Image For This Article) Got To Do With It?
Not much, really. After all, the Earth had been rotating around the Sun for billions of years before the ancient Brittanic culture built the ancient monument. However, there is one important feature of Stonehenge that makes its image come up in conversations whenever we’re talking about things like the Sun and the seasons: the stones are arranged in alignment with sunset on the night of the winter solstice, and the opposing sunrise of the summer solstice six months later.
Considering that construction of the early phases of the monument began about 3,000 years BCE, by an ancient culture that didn’t even have the wheel, that’s pretty impressive.
OK, But Why Aren’t The Days Uniform Year-Round?
Axial tilt, as your junior high school science teacher would be more than happy to tell you.
As University of Massachusetts astronomer Stephen Schneider explains to CBS News, “Earth’s axis is tilted 23.5 degrees relative to its orbit, and on December 21, Earth will be at the point in its orbit when the North Pole is tilted at its maximum away from the sun.”
— NWS (@NWS) December 20, 2017
Here in the northern hemisphere, the further north you are, the shorter the day will be. Up above the arctic circle, there will be no “day” to speak of, as the Sun won’t even break the horizon. Further south, the day will be longer, but even the southernmost locations of the northern hemisphere (that is, places nearest to, but north of, the equator) will have less than 12 hours of sunlight today.
Today Will Actually Be The Shortest Day In Human History (In The Northern Hemisphere)
The rotation of the Earth is slowing down, to the tune of a few millionths of a second per year, according to science blogger Colin Schultz. That means that, over the course of your lifetime, a year will be about two-thousandths of a second longer than it was when you were born. It also means that the length of the day today will be a few millionths of a second shorter than it was last year, making today the shortest day in human history in the Northern Hemisphere — a record that will be overtaken next year, and then the year after that, and so on.
Christmas Is Four Days From Now: Does The Winter Solstice Have Anything To Do With Christmas?
Probably. Long story short: The ancient Romans, as well as pre-Christian religions in Europe, all held the winter solstice in high regard, according to the History Channel. By the time Christianity came around, church leaders had a vested interest in getting the people excited about the holiday. Pope Julius I (c. 350) officially declared December 25 as Christmas Day, around the same time as pagan holidays, with the hopes that Christmas would be adopted and adapted by the Christians while still preserving some of their pagan traditions. To this day the Christmas tree, yule log, and the exchange of gifts all descend from ancient pagan winter traditions.