Happy Autumn Equinox! Today marks the astronomical beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. At the equinox, the Sun crosses the celestial equator, and day and night are nearly equal in length across most of the globe. The word “equinox” comes from the Latin aequus, meaning “equal,” and nox, meaning “night.” Why the Equinox Is Evidence Against a Flat Earth Around the equinox, the Sun rises almost exactly due east and sets almost exactly due west for ob