INTRO TO PHYSICS
March 20 or 21 is the vernal equinox or spring equinox (for the Northern Hemisphere), and the subsolar point is heading north, on its way to the Tropic of Cancer. September 22 or 23 is the autumnal equinox, or fall equinox (for the Northern Hemisphere); the subsolar point is on the way south. Throughout the year, daylength is 12 hours at equator. ................
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