If
you've ever wondered what hamsters and the French Revolution have to
do with the first day of fall, we've got the answers.
The
Northern Hemisphere will bid an official farewell to summer on the
evening of Sept. 22 and welcome in the fall. At precisely 10:29 p.m.
Eastern Daylight Time, the sun will be directly in line with Earth's
celestial equator (the equator projected onto the sky,) and day and
night will last roughly the same amount of time. From there, the days
will gradually grow shorter until the winter solstice, at which point
they will begin their journey back in the unending cycle that marks
our four seasons.
Welcome
to the autumnal equinox.
While
most of us realize that this special September day marks the start of
sweaters-boots-and-pumkin season (known to some as “fall”),
there’s much more to know about the date than first meets the eye.
Consider the following facts:
1.
The term equinox comes from the Latin “aequus” for "equal"
and "nox" for "night," since the equinox (both in
the spring and the fall) is the point where day and night are equal.
2.
That said, day and night equality is not exactly the case. While the
very center of the sun does indeed set 12 hours after it rises, the
day begins when the upper edge of the sun reaches the horizon (which
happens a little before the center rises), and it doesn't end until
the entire sun has completely set, explains The
Old Farmer’s Almanac —
meaning that the days are still a bit longer. It is a few days after
the September equinox when the span of equal day and night occurs.
3.
While the autumnal equinox usually falls on Sept. 22 or Sept. 23
every year, sometimes it goes askew. In 1931, it fell on Sept. 24.
Why? Because the planet takes 365.25 days to travel around the sun,
meaning that every so often, the Gregorian calendar and the sun’s
orbit collaborate to push the equinox back a day — but not very
often. The next fall equinox slated to happen on Sept. 24 will not be
until 2303.
4.
The full moon nearest the autumnal equinox is known as the "harvest
moon." During
this time of year the moon rises earlier in the evening, allowing
farmers to work further into the evening. In years when the harvest
moon occurs in October, it is called the “full corn
moon” because it often coincides with the corn harvest.
5.
Along with the vibrant flood of fall leaves ushered in by the
September equinox, the sky often has a colorful display of its own.
According to NASA, during the fall, geomagnetic storms happen twice
as frequently than the annual average, meaning that it is prime time
for viewing the aurora borealis.
6.
Brilliant leaves and geomagnetic storms aren’t the only things that
ramp up around the time of the autumnal equinox. The creature world
responds as well. Case in point? Animals at high latitudes go through
biological changes with the change of seasons. Take for example the
male Siberian hamster, a rodent that experiences a swelling of
the testes up to almost 17 times their normal size when the days
begin to get shorter.
7.
Between the years of 1793 to 1805, the fall equinox was the official
start of each new year according to the French Republican Calendar.
The French monarchy was abolished one day prior to the equinox in
1972, so the revolutionaries designed their new calendar to kick off
on the equinox. By law, the beginning of each year was set at
midnight, beginning on the day the autumnal equinox fell at the
Paris Observatory.
8.
The spring and fall equinoxes are the only two instances during the
year in which the sun rises due east and sets due west. So if you
aren’t that sure which way is which, use the equinox to note where
the sun is rising and setting, set your inner compass, and never get
lost again!
http://www.mnn.com/earth-matters/climate-weather/stories/8-things-you-didnt-know-about-the-autumnal-equinox
