In astronomy, the autumnal equinox (fall
equinox, September equinox, or southward equinox) signals the beginning of
autumn in the northern hemisphere: the moment when the sun appears to
cross the celestial equator, heading southward; the equinox occurs around
September 22–September 24, varying slightly each year according to the
400-year cycle of leap years in the Gregorian Calendar.
In the southern hemisphere, the equinox occurs at the
same moment, but at the beginning of spring. There are two conventions for
dealing with this: either the name of the equinox can be changed to the
vernal equinox, or (apparently more commonly) the name is unchanged and it
is accepted that it is out of synch with the season.
At the equinox, the sun rises directly in the east
and sets directly in the west. However, because of refraction it will
usually appear all slightly above the horizon at the moment when its
"true" middle is rising or setting. And for viewers at the north
or south poles it is moving virtually horizontally on or above the
horizon, not obviously rising or setting apart from the movement in
"declination" (and hence altitude) of a little under half a
degree per day - about 365.2/360 times the sine of 23.5 degrees.
In the northern hemisphere, before the autumnal equinox, the sun
rises and sets more and more to the north, and afterwards, it rises and
sets more and more to the south.
The autumnal equinox is when the Neopagan Sabbat of
Mabon is celebrated.
Also, Autumnal Equinox Day (秋分の日)
is an official national holiday in Japan, and is spent visiting family
graves and holding family reunions.
Culture of Autumn
|Apart from being the start of the school year,|
it is one of the seasons in which the film industry starts releasing
movies that are usually low-budget in scope, but worthy of artistic
achievement at academic institutions such as the Oscars and the BAFTA
awards (whose award ceremonies are held in late-February). Such movies are
considered low-key, deeper in content and more serious than their
big-budget, effects-laden summer counterparts. Autumn is the shortest and
least profitable season of the movies.
Autumn is also associated with the Halloween season, and with it a
widespread marketing campaign that promotes it. The film and music
industries use this time of year to promote movies and records that
closely associate with such holiday, and their releases begin in early
September but no later than 28 October, since their themes rapidly lose
strength once the holidays ends.
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