The Autumnal Equinox Is Next Friday

 

September 14, 2017



Astronomers at the Pisgah Astronomical Research Institute point out that at 4:02 p.m. EDT on Friday, Sept. 22, the sun will cross the celestial equator in the sky heading south. This will be the first moment of autumn.

What is the astronomical significance of this moment? At this moment the sun in its apparent path around the sky will stand directly over the equator of Earth. It is one of two times during the year when this happens, the other being on the first day of spring. These are the two days of the year when the sun is above the horizon for exactly half the day and is below the...



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