History of Fall: What is the Autumnal Equinox?
Equinox. Author’s photo from his iPhone
HISTORY OF THE FALL: What is the Autumnal Equinox?
This time of year represented New Year’s Day, according to the French Republican Calendar. However, since that calendar was only in use from 1793 to 1805, following the fall of the French monarchy in 1792, very few still celebrate this day.
Date of Autumn
Instead, September 22 or 23 marks the beginning of Fall or Autumn, associated with the Equinox. This word is composed of two Latin root words, aequus and nox, meaning “equal night,” which refers to the fact that daylight and nighttime are of equal duration.
What happens during Equinox?
Astronomical
When the plane of the Earth’s equator passes through the center of the Sun, metaphorically speaking, you have evennight, twice a year. This year, the astronomical autumnal equinox (Fall) occurs on September 22 at 18:20 UTC. This means Temps Universel Coordonne (or Coordinated Universal Time), if you speak French, roughly equivalent to Greenwich Mean Time if you’re British, Zulu Time if you’re a pilot. The Vernal Equinox occurs six months later.
Since each equinox occurs at the same time, whether in the Northern Hemisphere or the Southern Hemisphere, though the seasons are reversed, it is becoming common to refer to the (northern) vernal equinox as the March Equinox and the Autumnal Equinox as the September Equinox, thereby avoiding that annoying Northern Hemisphere bias.
During the Equinox:
- The Sun rises due east and sets due west
- The Sun rises at about 6 AM and sets at about 6 PM local time in most places on the planet except the poles
- In other words, daytime and nighttime are about the same length worldwide
- The center of the visible Sun is exactly above the Equator
- The edge between night and day (solar terminator) is perpendicular to the Equator, equally illuminating both the northern and southern hemispheres.
- Equinoxes are the only times when both the north and south poles are lit by sunshine at the same time.
Fall
Welcome September. Image by DALL-E 3
Meteorologically, Fall begins September 1. Meteorologists break down the year into three-month seasons based on annual temperature cycles. By that calendar, Spring starts on March 1, Summer on June 1, Fall on Sept. 1, and Winter on Dec. 1.
However, over the years, due to a confluence of influences, including, in part, truancy, sunspot activity, cosmic ray interference, and standardized testing, many students now return to classrooms in August – completely ruining the song “See You In September.”
Consequently, the end of Summer vacation is no longer observed following the Labor Day holiday.
Bill Petro, your friendly neighborhood historian
billpetro.com
