Yule

Merry Christmas for those who celebrate. While I grew up with Christmas, I don't find it particularly meaningful as an adult (although I still observe it for my wife and stepson). The winter solstice is, in many ways, a far more interesting seasonal event for me. Occurring last Thursday, December 21, at exactly 10:27 pm, it marks the point of maximum tilt of the Northern Hemisphere away from the Sun in our yearly orbit.

Many people, incorrectly, assume that the change in seasons has to do with our distance from the Sun. This is incorrect as the Earth is closest to the Sun (perihelion) on January 2, 2024 (aphelion, the furthest point, is six months later in early July). The seasons are due to the tilt of the Earth's axis as it orbits the Sun. When the Northern Hemisphere is tilted away from the Sun, the sunlight at our mid-latitudes can't reach halfway around the Earth leading to a 9 hour day here in Ulster County, NY. In addition, the Sun is at a lower angle in the sky (about 25º altitude) meaning the incoming solar energy (insolation) is smeared out more than in the summer when the Sun is higher in the sky (around 70º of altitude with 15 hours of daylight in late June). It's the tilt, not the distance that causes the seasons.

There's a reason why almost all ancient cultures (at least in the mid-latitudes) observed the solstices - they are real events with a real impact on our lives. They especially impacted ancient people since solstices and equinoxes, along with the cycle of phases of the Moon, defined all early calendars (and even some religious calendars today).

I always try to mark the winter solstice with a fire in my backyard fire pit after the Sun goes down. Depending on the outside temperature, some friends or family may or may not join me. For me, like my northern European ancestors, the winter solstice is a time to celebrate as it marks the turning point where the days start to get fractionally longer again even though the worst parts of winter are yet to come. In ancient times, it used to be, and still should be in my opinion, the official New Year's Day. January 1 is an artificial construct due to political considerations in the Roman Empire.

The decreasing hours of daylight in the winter really gets to me. I have to always make an effort to get outside and get some sunlight during these shorter days - something difficult to do when I sometimes find myself inside working for most of those daylight hours and the persistently cloudy Hudson Valley winter days.

So, no geology in today's blog post (although talking about the seasons is basic Earth science) but some of my outdoor winter excursions may well be to geologic locales for future posts!