CENTRAL ILLINOIS (WCIA) – Today is the “Fall Equilux” for Central Illinois.

That’s different than the Fall Equinox, which occurred on September 22nd and is when Fall officially starts.

The Fall equinox, also known as a autumnal equinox, is when the sun’s rays are directly over the equator. Equinox means “equal night” in Latin.

However, due to the angle and curvature of the earth, not everyone sees equal amounts of light and dark on the equinox.

For Central Illinois, our Spring Equilux is a few days before and our Fall Equilux is a few days after each corresponding Equinox.

Equilux means “equal light” in Latin, and is used when the daylight hours and the nighttime hours are equal in length, at or close to 12 hours.

The reason for this is because of a phenomena called Atmospheric Refraction.

Our atmosphere refracts sunlight about half a degree upward, bending it from below the horizon up to our eyes. This means we see the sunrise before the Sun is actually above the horizon.

The same is true for the sunset; we see the Sun after it has physically set.

The atmospheric refraction means the sunrise time is actually a touch earlier and the sunset time a touch later.