It’s a common conception that the Equinox marks a day when the length of nighttime and daylight is exactly equal, 12 hours each. But, it’s the Equilux – which happens today, 28 Sept. – when that it actually true.
Each year, there are two Equinoxes and two Equiluxes – one in March and the second in September.
Tiyen Miller, of the Cayman Islands Astronomical Society, explains the difference.
“Today in the Cayman Islands is the Equilux. Today, the 28th of September, the time that passes from the first glint of sunrise to the last sliver of sunset is the same as the time that passes over the night.
“Now, this sounds a bit like Equinox, but Equinox measures from when the middle of the sun reaches the horizon in the morning to when the middle of the sun descends over the horizon in the evening but, of course, by the time the middle of the sun is up, you’ve already had light coming for a while when the top edge comes up.
“So today is really the ‘equal’ equal day.”
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