Wednesday, September 21, 2016

Autumnal Equinox is Here!

The autumnal equinox will occur tomorrow, September 22nd. We all know that means fall officially begins (at 9:21am to be exact), but what else does that phrase mean? The word "equinox" is derived from Latin. In Latin, the prefix "equi" means equal, and the word "nox" means night. Putting these two together results in a word that literally means "equal night." And, if equal night occurs, equal daytime would automatically occur as well. In other words, the autumnal equinox is a day that features essentially equal daylight and nighttime for both the northern and southern hemispheres.

The reasoning for the equality is simple: the sun's rays hit directly at the equator, which leads to 12 hours of daylight and 12 hours of nighttime. It's important to know, though, that it is not exactly 12 hours of each, but it is very, very close. The autumnal equinox always occurs in late September in the northern hemisphere. Once we pass the 22nd, we will start to lose daylight each day through the winter solstice, which occurs in late December. That day features the northern hemisphere's shortest day in terms of daylight of the entire calendar year.

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