First day of Fall, today, September 23, 2015

Time USA/Noal Feeney, 9/21/15. "Here's why Wednesday is the first day of Fall. The autumnal equinox is September 23rd."

Leaves turning orange
and red, falling. Not here yet

"There are plenty of annual events that mark the beginning of fall: the Labor Day holiday, the arrival of Pumpkin Spice Lattes at Starbucks, the changing colors of the leaves, the first overwhelming urge to wear a sweater since the end of spring. But there’s only one official start of the season, and that’s the autumnal equinox, which arrives this Wednesday, Sept. 23., according to the U.S. Naval Observatory.

Official first day of Fall, autumnal equinox

As TIME has explained before: “While that might sound like a name of a place where hunks sculpt their biceps, the word comes from the Latin term aequinoctium, meaning equality between day and night (aequi = equal and ­noct = night). That is what [the equinox] is after all: one of the two periods of the year when the sun crosses the equator and the days and nights are in equal length all over the earth.”

If you want to get very technical, day and night aren’t actually perfectly equal on the fall equinox. That’s because the equinox is officially marked by the day the center of the sun sets exactly 12 hours after it rises everywhere in the world—while the length of a day is measured differently, based on the time the very top of the sun rises and sets, according to the U.S. Naval Observatory. But the measurements are close enough that day and night are approximately equal for several days around the equinox.  While it’s technically still summer until Sept. 23, that doesn’t mean it hasn’t already started feeling like fall—just look at this TIME interactive graphic that tracks the arrival of temperatures we most associate with autumn."

Related, Wikipedia/September Equinox.  "The September equinox (or Southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Due to differences between the calendar year and the tropical year, the September equinox can occur at any time from the 21st to the 24th day of September.  At the equinox, the Sun rises directly in the east and sets directly in the west. Before the Southward equinox, the Sun rises and sets more and more to the north, and afterwards, it rises and sets more and more to the south."  Dictionary.com/Equinox."1. the time when the sun crosses the plane of the earth's equator, making night and day of approximately equal length all over the earth and occurring about March 21 (vernal equinox or spring equinox) and September 22 (autumnal equinox).  2.either of the equinoctial points."   

Note photograph/graphic.  Leaves from Mackinaw City, MI, "Fall shoppers festival." Equinox from the Wikipedia article above.

Posted by Kathy Meeh