The Vernal Equinox: What is it?
It’s the official start of spring! The Spring or Vernal Equinox will occur on March 20th of this year at 4:57 p.m. But what’s actually happening at this time?
An equinox occurs twice per year (approximately March 20th and September 22nd), when the plane of the earth’s axis passes the centre of the Sun. The tilt of the earth’s axis is inclined neither towards nor away from the Sun. At this time, night and day are about equal length and the Northern and Southern hemispheres are equally illuminated. Hence, the term equinox derived from the Latin aequus (equal) and nox (night).
In March, the subsolar point, the place on earth’s surface where the centre of the Sun is exactly overhead moves northward from the Equator. This is the Vernal Equinox, ver being Latin for Spring. In September, the subsolar point moves southward from the equator. This is the Autumn Equinox, autumnus being Latin for autumn.