Today is the equinox. The autumnal equinox, to be precise. Astronomically-speaking, the equinox is more than just a box marked on a calendar or the start to fall.
Astronomers define the autumnal (fall) equinox as the moment when the Sun crosses the Celestial Equator, heading from the north to the south. And what is the Celestial Equator? It’s just the projection of the Earth’s equator onto the heavens. As the Earth rotates, the Celestial Equator appears as the midpoint of the sky’s motion. (taken from New York City Astronomy)
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The fall equinox - September 22, 2009
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