Today is the first day of Fall in the Northern hemisphere, and at 3:50 am Eastern Time (7:50am UT)  was the beginning of the September equinox. At 3:50 am ET, the Sun crossed the celestial equator.

“An equinox is commonly regarded as the instant of time when the plane of Earth’s equator passes through the center of the Sun. This occurs twice each year: around 20 March and 23 September. In other words, it is the moment at which the center of the visible Sun is directly above the Equator. … On the day of an equinox, daytime and nighttime are of approximately equal duration all over the planet. They are not exactly equal, however, due to the angular size of the Sun, atmospheric refraction, and the rapidly changing duration of the length of day that occurs at most latitudes around the equinoxes.” [Wiki.]

At my location (39.66N, 75.67W) sunrise was at 6:51 am and sunset will be at 6:59 pm, making the day 12 hours and 8 minutes long. Continue reading →