Yesterday was the first day of spring in the Northern Hemisphere and also the vernal equinox. This image from the Meteosat-9 satellite shows Earth from space on the equinox. As the New York Times explained, the spring equinox is a point in Earth’s orbit where the sun shines directly above the Equator, creating nearly equal periods of daytime and nighttime across the globe.
Greg Redfern, a solar system ambassador at NASA’s Jet Propulsion Laboratory, said “Only on the equinoxes do we get that exactly straight terminator,” referring to the line separating daylight from the darkness of night that you can see in the photo above.