Today – September 22, 2009 – marks the official beginning of Autumn in the northern hemisphere. Astronomically speaking, it is the autumnal equinox, one of only two days per year in which night and day are of approximately equal length and the Sun crosses the celestial equator. (If you’re curious, the Sun crosses the equator from north to south during the autumnal equinox, and south to north during the vernal/spring equinox.) But most of us don’t need an astronomer to tell... [Continue Reading]