Equinox

I've always had this notion that the vernal and autumnal equinoxes (equinoxi?) were called equinox because on those days, we had equal night and day.  Imagine my disappointment, nay, my feelings of betrayal and dismay, when, a few years ago, I decided to check.  On the equinox, I looked at our sunrise and sunset times, and discovered ... I'd missed it.  The day that we had had equal day and night had been a few days prior†. 

Today is our equinox, as in the day we have equal day and night, here near the 45th parallel north.  See that?  Sunrise at 7:19 a.m.*; sunset at 7:19 p.m.  Equal.

Astronomically speaking, an equinox is the moment when the sun crosses the equator**, which means that the Earth's axis is perpendicular to the sun's rays, which should mean, in theory, that everywhere on earth gets equal amounts of light and darkness.  And it's true that everywhere*** on earth gets approximately equal amounts of light and dark on the day of an equinox--it's just not quite equal.

But, of course, there are other factors involved, including the fact that light is stronger than, and overcomes, darkness††.  I mean, there are science-y words for it, but that's what it comes down to.

Fun fact: Amundsen-Scott South Pole Station, Antarctica switches from polar day (when the sun is always above the horizon) to polar night (when the sun is always below the horizon) around March 23, which is also not the equinox.  

* * * 

† We also do not have our longest night on the winter solstice or our longest day on the summer solstice.  Talk about feeling betrayed.

* That feels untrue, since it's over an hour later and I haven't seen the sun****

** The celestial equator, which is an imaginary line in the sky above the equator.

*** Not the south pole, obviously.

**** Because it's cloudy, not because the sun didn't rise, but it feels like the sun didn't rise. 

†† The presence of something (light) drives out the absence of something (darkness).