Wellesley Celebrates the Official Start of Fall on the Autumnal Equinox

Fallen autumn leaves with a view of Lake Waban
September 22, 2017

As changing foliage and shorter days are making it feel like fall on campus, we’re pondering the astronomical definition of an equinox. According to NASA, an equinox occurs the moment the sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator.  The Autumnal Equinox marks the first day of astronomical fall in the Northern Hemisphere, and astronomical spring in the Southern Hemisphere. It is one of two days a year when day and night are nearly equal lengths across the globe.  The equinox will occur today, Friday, September 22, at 4:02 p.m. EDT.