STORMTRACKER SCIENCE: What is an Equilux?

Weather

CLARKSBURG, W.Va. – The beginning of Fall has come and passed in north-central West Virginia as the leaves have already begun changing colors.

People normally associate the Autumnal Equinox (also known as the beginning of Autumn or Fall) with an equal length of day and night, but that is not always the case.

Autumn at Valley Falls State Park. Picture: Scott Sincoff

At the equinox, the Sun’s angle is measured from when the center of the sun is at the horizon and is 12 hours sunrise to sunset and vice versa. However, the Equinox occurs when the upward edge of the Sun is visible first at sunrise while ending at sunset.

Autumn 2019 at Blackwater Falls State Park. Picture: Scott Sincoff

Because of the refraction (or bending) of the Sun’s rays, extra daylight is added is still visible once the Sun has set (known as twilight). This allows for extra seconds and minutes during the first few days of Fall.

In Autumn, this means that the time when day and night are actually equal happens anywhere from one to four days after the equinox.

This is called the Equilux, which means “Equal Light” in Latin. It means that during the year, we should get a bit more light than dark.

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