Complex Numbers

December

Another turn of the wheel.

https://www.vox.com/science-and-health/2018/12/18/18144477/winter-solstice-2018

As I wrote last month, this is one of the things that, were we so inclined, we could all agree on. It affects the entire human race (at least for now; I'm still hoping for space travel), even if its effects depend on your current latitude.

I should add a couple of observations to the article I linked above.

First, while the vast majority of humans live in the Northern Hemisphere, that's no excuse for hemispherism. Most of us see it as the Winter Solstice but, as noted, it's the Summer Solstice in the south. To avoid being exclusionary, I've seen it referred to as the December Solstice. A better name - one that's not tied to our arbitrary calendar - might be the Capricorn Solstice. However, that would make the other solstice the Cancer Solstice, and I can see people objecting to that.

Second, unless I missed it (I tend to skip boring parts, which is one reason I don't like internet videos), it doesn't define what "solstice" really means. Yes, it says "Technically, the solstice occurs when the sun is directly over the Tropic of Capricorn, or 23.5° south latitude." But the word is from Latin: sol (sun) + stice (from a root that means 'stationary'). So literally it means like, "the time the sun stands still." Which is pretty cool. Of course, the sun doesn't actually stand still - figuratively or literally - it's a bit more complicated than that. From the point of view of any observer on Earth, each day when the sun reaches its highest point in the sky (known as local noon, which is usually not when the clock says noon), it appears slightly more to the south between late June and late December. As the calendar approaches the December solstice, the sun's apparent location at local noon drifts a bit further south each day. On the solstice itself, it's at its southernmost point. Technically, the solstice occurs at local noon at whatever longitude the sun happens to be crossing when it's at zenith at the Tropic of Capricorn.

Yes, I know. If I'd been reading this, I'd have skipped the last paragraph.

Third, did you see the gif in the linked article with the time-lapse of Earth from space? It's pretty cool. With a little digging, I found that the satellite that shot these pictures is a weather satellite in geostationary orbit. When I saw the gif, my first thought was "that satellite is directly over 0/0." 0/0 being the point where the Prime Meridian crosses the equator. It's in the Atlantic, off the coast of Nigeria. I'm not so jaded that I find photos taken from geostationary satellites to be a mundane thing. Really, I'm not sure whether it's over the actual origin or not, but it's pretty close.

Anyway, science in general is cool, astronomy in particular is fascinating, and culturally, we have a long history of marking the solstices and equinoxes. As I've mentioned before, I don't observe Christmas, so the day I care about is the solstice. It's a time to consider rebirth and renewal; the moment when, just as everything seems to be about to plunge into eternal darkness, there's the promise of more light to come. It's more interesting to me than the very arbitrary New Year's Day (the proximity of which to the solstice isn't accidental), and more meaningful.

In the past, I've marked it for myself by staying awake through the longest night, maintaining a vigil for the returning, invincible sun. I think I might revive that tradition for myself on Friday.