Happy #equinox and happy #fall to all! #Repost @nasa_eo ・・・ First Day of Fall 2016 One of the most frequently misunderstood concepts in science is the reason for #Earth’s seasons. As we experience the September #equinox today we thought we’d offer a space-based view of what’s going on. Around 6 a.m. local time each day, the Sun, Earth, and any geosynchronous satellite form a right #angle, affording a nadir (straight down) view of the terminator, the edge between the shadows of nightfall and the #sunlight of dusk and dawn. The shape of this line between night and #day varies with the seasons, which means different lengths of days and differing amounts of warming #sunshine. (The line is actually a curve because the Earth is round, but satellite #images only show it in two-dimensions.) The Spinning Enhanced Visible and Infrared Imager (#SEVIRI) on #EUMETSAT's Meteosat-9 captured these views of Earth from geosynchronous orbit. The images show how sunlight fell on the Earth between Septem...