At 0530 Universal Time on December 22 (which translates into half past midnight Eastern Time and 11:30 PM December 21 Central Time, etc.) the Earth's axis will be tilting as far away from the sun (23.5°) as it ever gets in its annual orbit around our star. That’s the moment of the winter solstice.
While the day
itself remains the same length as always (24 hours), the amount of daylight
is as short as it gets (in the Northern Hemisphere), while the hours of darkness are as long as they ever get. This is because, in the 6 months leading up to today, the Sun has reached its apex in the sky (which always occurs at noon every day) at a progressively lower and lower point, seeming to be heading toward the southern horizon.
To ancient people, who spent way more time outdoors than we do today and thus were more in tune with nature, it looked as if the Sun might be leaving them. To superstitious
ancient people (which was most of them) there was always the possibility that it might disappear altogether (which actually does happen above the Arctic Circle) but moreover never come back, leaving them in the cold and dark forever.
Thus, when the Sun's southward journey seemed to slow and finally stand still (which is what "solstice" literally means), heralding its return, bringing warmth, comfort, and renewed greenery with it, it was cause for rejoicing. Besides, if they didn't pig out on all that food they'd stored up, it might rot anyway, so let's dig in, gang. In the immortal words of the Beatles, “Here comes the Sun, dooten doodoo, here comes the Sun, and I say ‘It’s all right!’.”
That why, all over the Northern Hemisphere thruout all of recorded history, pretty much everybody has been more than happy to take advantage of the excuse to party and celebrate at this time of year. In fact, lots of them made the occasion part of their religious observances. (You may be familiar with some of them, tho hardly anybody celebrates Saturnalia, Sol Invictus [unconquered Sun], or Mithra's birthday any more.)
So, when anybody asks about “the reason for the season”, look no further. This is it.
I’d like to take advantage of one more seasonal tradition and extend a traditional good thot to everyone:Peace on Earth, good will toward all.