What is September Equinox? It was easy for our ancestors to figure out that every year, one day had the fewest hours of daylight, and one day had the most, and these made an easy way to divide the year in half. Since i love organizing things, i divided it again, marking days halfway between the two.
The Equinoxes : the day when there’s equal day and night. Except day and night on the equinoxes isn’t equal. And they’re not halfway between the shortest and longest days of the year. The equinox probably isn’t what you think it is.
Instead of being a whole day, the equinox is one very specific moment, when Earth’s axis isn’t pointing toward or away from the sun at all, which is also when the center of the sun crosses the equator.
But if exactly half of Earth is bathed in darkness and the equator is perpendicular to the sun, then why doesn’t the equinox have equal day and night? Because we mark “sunrise” when the top of the sun rises above the horizon, and “sunset” doesn’t happen until the last sliver disappears, “day” is several minutes longer than “night” on the date of the equinox.
If the sun were a point, instead of a disk, this wouldn’t be a problem, but even then, the sun would appear to be up in the sky for longer, because near the horizon, Earth’s atmosphere acts like a lens, bending the sun’s rays to make them visible even when it’s already dropped below.
As a result, the date when night and day are exactly equal, the equinox, happens a few days earlier than the equinox in March, and a few days later in September, although precisely when depends on your latitude.
And because Earth’s orbit is elliptical, the solstices and equinoxes don’t divide the year into even halves or quarters. Because of gravity, as Earth gets closer to the sun, it travels slightly faster in its solar orbit, which means there are more days on the June side of the equinoxes than on the December side. and so on.
For the same reason, in the northern hemisphere, we get a few more days between the summer solstice and the winter solstice than vice versa. So while the name might mean “equal night”, each equinox has a bit more day, as sure as the sun rises in the east and sets in the west Stay curious. Since this happens around the month of September, it’s known as September Equinox.
The next time someone is talking about space and research, do share this article about September Equinox. Feel free to reach out for more information on this article or anything related to Digital Marketing.