by Bennett Horton Jr.

Created on: March 27, 2010

What Happens at the Vernal Equinox

The word “equinox” comes from the Latin for equal night.  It might just as accurately have been named “equidies” (equal day), for at the time of an equinox the periods of sunlight and darkness in a single day are of nearly equal length (exactly equal length on the equator).  This occurs because of the earth’s tilt on it’s axis as it orbits the sun, which is why we have seasons.

When the earth’s orbit brings the sun’s equator directly above the earth’s equator, an equinox occurs.  There are two: vernal (which begins spring on March 19, 20, or 21) and autumnal (which begins fall and falls on September 22 or 23).  “Ver” and “autumn” are again from the Latin.  There are two other pivotal points in the earth’s orbit: the solstices, which begin summer and winter.  The orbit is elliptical in shape, and one could say the solstices occur at each end and the equinoxes at the two points in the middle.

From a practical point of view, what happens at the vernal equinox is the days – periods of sunlight – start getting longer than the nights if you live in the northern hemisphere.  (All of this is reversed in the southern hemisphere where spring begins in September.)  This is why the plants bud out and eventually bloom, and life in general becomes more cheerful.  Many of our present day customs to celebrate this time of year, e.g., painting eggs with bright colors, go back far into antiquity and were not associated with any of today’s organized religions unless you count nature worship.

Equinoxes can occasion another phenomenon: storms.  The sun moves south to north or vice versa faster than at any other time of year (2.5 degrees of arc or more in a week).  This rapid change in the sun’s position produces large variations in the patterns of warm and cold air masses and viola: violent storms can result.  Sailors have long known to beware the “equinoctial gales”.

Understandably, ancient people paid close attention to the sun’s position relative to the earth.  When the winter solstice occurred they knew they wouldn’t be doomed to eternal winter (though winter was just beginning, the days started getting longer again).  When the vernal equinox happened, this was a guarantee that life would reawaken and be renewed for another growing season. 

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