Today is the first day of spring in the North Hemisphere. And it comes with a vernal equinox. It occurred at 1:48 EST marking the beginning of spring 2008. This season will last until June 21, summer solstice.
What is a Vernal Equinox?
According to Wolfram.com
The date (near March 21 in the northern hemisphere) when night and day are nearly the same length and Sun crosses the celestial equator (i.e., declination 0) moving northward. In the southern hemisphere, the vernal equinox corresponds to the center of the Sun crossing the celestial equator moving southward and occurs on the date of the northern autumnal equinox. The vernal equinox marks the first day of the season of spring. The right ascension at the vernal equinox originally was in the constellation Aries and the point of crossing was known as the first point in Aries (now actually in Pisces because of precession).
So, you see, it’s an astronomical event that serves us determine our seasons. In the Southern Hemisphere we can observe the autumnal equinox which marks the beginning of fall.
Source: http://toppayingideas.com/blog/2008/03/20/spring-starts-with-vernal-equinox-2008/
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