What exactly is an equinox?
Twice a year, either on March 20 or 21 and Sept. 22 or 23, the sun's rays shine directly over the earth's equator. March is known as the vernal equinox, or spring equinox in the Northern Hemisphere. September is known as the autumnal equinox.
What occurs during the autumnal equinox?
During the autumnal equinox, day and night are balanced to about 12 hours each all over the world. Earth's axis of rotation is perpendicular to the line connecting the centers of the Earth and the sun.