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Autumnal Equinox — Infoplease.com
In the language of science, an equinox is either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. For the rest of us, it's one of two ...
Equinox - Wikipedia, the free encyclopedia
Vernal point and autumnal point are the points on the celestial sphere where the Sun is located on the vernal equinox and autumnal equinox respectively (again, the seasonal attribution ...
Autumnal Equinox -- from Eric Weisstein's World of Astronomy
The date (near September 22 in the northern hemisphere) when night and day are nearly of the same length and Sun crosses the celestial equator (i.e., declination 0) moving ...

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Autumnal Equinox

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Autumnal Equinox, one of two times of year when the Sun’s position makes day and night of nearly equal length in all parts of the Earth. The autumnal equinox, which usually occurs on September 22 or 23, marks the beginning of the fall season in the Northern Hemisphere.

For information on:

astronomical aspect of the autumnal equinox, see Ecliptic; Harvest Moon

early descriptions of the autumnal equinox, see Hipparchus; Copernican System

prehistoric structure possibly used for predicting the autumnal equinox, see Stonehenge: Purpose of Stonehenge

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