Wednesday, March 20, 2013
Why do the seasons change? The four seasons are determined by shifting sunlight (not heat!)—which is determined by how our planet orbits the Sun and the tilt of its axis. According to the Old Farmers Almanac:
On the first day of spring—the vernal equinox—day and night are each approximately 12 hours long (with the actual time of equal day and night, in the Northern Hemisphere, occurring a few days before the vernal equinox). The Sun crosses the celestial equator going northward; it rises exactly due east and sets exactly due west.