Welcome to the Solstice

Sun solstice

We’ve got fun and games.

Okay, well, not many people have fun and games literally today, which fact always seems mildly puzzling to me.  Why do we do our solstice-based celebrations–Christmas mainly, in the “West”*–a few days after the Solstice proper, which is today, and generally falls on roughly December 21st, not on the 25th?  It’s certainly nothing to do with Jesus’s actual birthday, which most scholars seem to agree was probably nowhere near the Winter Solstice, and was more likely to have been in the summer, though even that’s far from certain.

Maybe the idea is that the days have finally started to become longer by the 25th, and so we really have something to celebrate then?  But this reasoning seems a little dicey.  It’s true that, today, or at least at precisely the time of the Solstice, the momentary rate of change of day length is zero, as is always the case at either a minimum or maximum of any smooth function curve.  And, the day “length” being a sine-like curve, its rate of change (its derivative) is a cosine curve, and the cosine at the minima and maxima of a sine curve is zero–as it must be, it being a derivative of a smoothly varying function.

As a practical matter, this means that the difference in day length between today and Christmas is very small.  I could look up the amount, but I’m not going to bother, since the specifics are beside the point.  The point is, it’s vaguely nice to know that the days are beginning to get “longer” again, but it’s not going to be a noticeable difference for quite some time.  The length of daylight on Christmas isn’t much different from the daylight length on the 17th of December, which was pretty short.  The change doesn’t really start to speed up until we head toward the equinox, for which the sine is at zero, and the cosine is at a minimum or maximum (the sine being the derivative of the cosine just as the cosine is of the sine).  And goodness knows that there are many times when I don’t really want to be alive to see it.

Be that as it may, I still wish you all a good Solstice and subsequent holidays, and I hope you’re all as happy as you can be.  I certainly hope you’re happier than I am.  That’s not a high bar to clear; I’m a proper downer.

For those in the Southern hemisphere, of course, it’s the Summer Solstice today, and you can “look forward to” the days now getting shorter, so to speak.  But don’t worry; here too the change won’t be noticeable for quite some time.  Enjoy your Christmas and New Years (or any other Solstice-proximate holidays you might celebrate) on the beach or in a park or in your yard with a barbecue, or however you all do it.

As for me, well, as is often the case at this time of year, I really don’t hope to see another Solstice, winter or otherwise, ever again.  So far that’s been a disappointed hope, if you will.  We’ll have to see what happens, I guess.

Which is always the case.

hengeworthy


*I put that in scare quotes because it’s a thoroughly arbitrary distinction to call one part of the world West and another part East.  West and East are fundamentally relative measures, as opposed to North and South, which are both relative and absolute.  Which one you call North and which South is arbitrary, but the distinction on a spinning globe is a real one…the most extreme points are at the “axes” (that’s plural of axis, not of axe), and if you try to keep going once you reach the North Pole, you’ll now be going South.  Not so with West or East.  You can keep going West or East forever, in principle.

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