Updated March. 4, 2014
MARCH 20TH is the first day of spring, or vernal equinox, as astronomers would have it — vernal meaning "of or pertaining to spring," equinox meaning "equal night." As the angle of the earth's inclination toward the sun changes throughout the year, lengthening or shortening the days according to season and hemisphere, there are two times annually when day and night are of more-or-less equal length: the spring and autumnal equinoxes. These celestial tipping points have been observed for thousands of years and given rise to a considerable body of seasonal folklore.
Cycle of death and rebirth
Spring has been celebrated throughout human history as a time of organic and spiritual rebirth following the "dying of the year" in winter. The ancient Germanic festival of Ostara (in honor of the goddess also known as Eostre) celebrated the cyclical return of light and life with fertility rituals and symbols, some of which still survive in the modern observance of the Christian holiday Easter, which traditionally falls on the first Sunday after the first full moon after the vernal equinox.
The egg being the most literal and obvious of all fertility symbols, ancient eggish customs survive not only in the form of egg rolling and Easter egg hunts, but also in the quaint superstitious belief, most often attributed to the Chinese, that you can stand raw eggs on end on the first day of spring. Apparently this derives from the notion that due to the sun's equidistant position between the poles of the earth at the time of the equinox, special gravitational forces apply.
Looked at with a skeptical eye it doesn't make a whole lot of sense, however. While it's true that on both the spring and the fall equinox the earth's axis is perpendicular to the sun, making day and night of equal length, there's no scientific reason to suppose that such an alignment exerts any perceptible effect on solid objects here on earth. Plus, if the equinox can cause this curious gravitational anomaly, why not others? Why don't we see people standing pencils, lollipops, and foot-long hot dogs on end on the first day of spring? Why just eggs (well, okay, and the occasional broom)?
To be taken with a few grains of salt
I'm not saying it can't be done — standing raw eggs on end, I mean — it certainly can, but it takes patience, eggs of just the right shape (trial and error is the only way to find them), a pinch of salt if all else fails, and — here's the biggest "secret" of all — it works equally well any day of the year (see instructional video).
Dr. Phil Plait's Bad Astronomy home page rightly condemns all this talk of equinox-related gravitational forces as unscientific hooey, but don't let that stop you from gathering friends and family around to try balancing eggs yourself.
At the risk of being boiled and dyed for heresy, I daresay there is more to life than science.