It’s that time again. If you are in the northern hemisphere on planet Earth, today is the Fall Equinox.
Autumnal Equinox 2023: First Day of Fall | Facts, Folklore & More | The Old Farmer’s Almanac
After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier. This ends with the winter solstice, after which days start to grow longer once again.
The word “equinox” comes from Latin aequus, meaning “equal,” and nox, ”night.” On the equinox, day and night are roughly equal in length.
Why just “roughly” equal in length?
Why day and night aren’t equal length on an equinox
Firstly, the sun has a size—it’s not just a point in the sky.… Secondly, the Earth’s atmosphere refracts (bends) sunlight.
What does the ebb and flow of axial luminescence look like from space?
For more on the “why” of seasons, check out this explainer:
What Causes the Seasons? | NASA Space Place
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J.R. Johnson 
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