autumnal equinox

“An equinox occurs twice a year, when the tilt of the Earth’s axis is inclined neither away from nor towards the Sun… The name “equinox” is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day have approximately equal length.” (Wikipedia)

Tomorrow is the autumnal equinox, the first official day of fall, and the official start of longer nights and shorter days. While the days have been getting shorter all summer long, it’s only in the last few weeks that it’s been noticeable. Our alarm has started going off before there is light in the sky these days, and that means that it’s fall.

I was curious to learn this year that the equinox didn’t fall on the (I thought) traditional 21st of the month. That was always how I kept track of solstices and equinoxes–those equidistant markers of seasons. Curious as to why, I did a little reading and also learned that our common definition of equinox is not totally accurate: in fact, when the day and night are both closest to 12 hours each it is called an equilux. Equiluxes are a phenomenon of time. Equinoxes are specific points in time in which the center of the sun can be seen directly overhead. Equinoxes have to do with the spacial relation of the Sun’s center and the Earth’s core. Who knew?

All that to say that today is the official last day of summer. And it looks like this weekend could be one of the last sunny ones too–it’s supposed to start raining on Monday. Enjoy the sun! And happy fall, everyone.

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