In reality, the length of days and nights are not equal at the equator…they’re close, but not exactly equal in length. We had a September 24 equinox in 1931, but won’t see another one of those again until the year 2303.
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What is an equinox exactly? The Fall Equinox, as pictured in this NASA Earth Observatory photo, is caused by the tilt of the earth’s rotating axis. Weather folks consider the first day of autumn to be September 1, the first day of winter December 1, the first day of spring March 1 and the first day of summer June 1. The Earth is moving so quickly around the sun that the length of day/night will change quickly. “It’s really not when the day and the night are of equal length, although that’s what we think of – it’s really that moment is when the sun is on the equator at local noon”, Matthew Holman, an astrophysicist at Harvard University, told National Geographic a year ago. For these reasons above mid latitude areas, like here, don’t actually have 12 hours of day and night until a few days after the Autumnal equinox and a few days before the Vernal equinox.
Though equinox means “equal night” in Latin, both of Earth’s hemispheres get slightly more than 12 hours of daylight on the equinox.
Why? This is the moment when the Sun crosses precisely over Earth’s equator as it heads south for the season. First, “sunrise” and “sunset” are defined as when the Sun’s top edge – not its center – crosses the horizon.
During the equinox, the North Pole points neither toward the sun nor away from it.
“The equinox is defined as the time of an event”. Civil twilight refers to the time before sunrise and after sunset when the sun is within 6 degrees of the horizon.
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Eastern Daylight Time: 10:21 a.m. It may sometimes also fall on 23rd of September.
