#equilux

Today is 12 hours long! The day and night are equal lengths!

Doodles I don't wanna post in the good account

My friend shared with me a song saying "this is just sollux/equius" and my monky brain activated

The next equinox is coming up in just under seven hours at the time of this posting, at 2023-09-23 06:50 UTC

(See when the impending southward equinox will be in YOUR timezone!)

Many folks have the impression that the equinox is "when day or night are equal" but actually, an equinox is a moment in time! It's when the sun is directly above the Earth's equator, and happens twice a year.

Above image of the moment of equinox from wikipedia.

The day that day and night are equal is known as the equilux and happens in different places on different days (depending on latitude).

And, if you are close enough to the equator, you NEVER get a day less than 12 hours and a day is ALWAYS at least a few minutes longer than night! This is because of atmospheric refraction.

Speaking of atmospheric refraction, this also causes the sun to be above the horizon at BOTH the north and south poles for a short time before and after an equinox!

According to what I've been able to determine (with this sunrise and sunset calculator) at the south pole, the sun rose September 21 at 03:39 UTC, and the sun will set at the north pole on September 25 09:58 UTC!

How did I not know about the equilux before?

Despite common belief, day and night are not equal on the Equinox. The Equinox is when the sun crosses the the celestial equator, so it rises due east and sets due west.

Day and night are equal lengths on the Equilux, which is either a few days before or after the Equinox.

The post above also has a link to help you find the Equilux in your location.

HAH - On the equinox the length of day and night are only nearly equal. This is because Equinox occurs when the center point of the sun’s disc crosses the celestial equator. 

Because the sun’s light is refracted by the Earth's atmosphere, the sky gets light before the sun rises, and remains light after it sets, providing additional daylight.

The equilux is when day and night are of equal length and occurs a few days before the spring equinox, and a few days after the autumnal equinox.