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#1 2015-09-22 13:46:26

ganesh
Administrator
Registered: 2005-06-28
Posts: 23,450

Equinoxes...

An equinox is an astronomical event in which the plane of Earth's equator passes the center of the Sun. Equinoxes occur twice a year, around 21 March and 23 September.
The equinoxes are the only times when the subsolar point (the place on Earth's surface where the center of the Sun is exactly overhead) is on the Equator, and, consequently, the only times when the Sun is at zenith over the Equator. The subsolar point crosses the equator, moving northward at the March equinox and southward at the September equinox. The equinoxes are the only times when the solar terminator is perpendicular to the Equator. As a result, the northern and southern Hemispheres are equally illuminated.

equinox_solstice_610.jpg


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