|MadSci Network: Astronomy|
I had never heard of this phenomenon before but I did quick search on the web and Yahoo has a whole category of links about it.
Unfortunately, although it sounds like a fun experiment, I'm afraid it's an urban legend. There's no physical reason why the Spring Equinox (Mar 21) should affect an egg and it's just as easy to balance one on its end on any other day of the year.
For a discussion of this, please look at Phil Plait's egg-spinning page , which even includes pictures of eggs standing on end on Oct 25th (neither an equinox nor a solstice).
Jim O'Donnell, MadSci Admin
Try the links in the MadSci Library for more information on Astronomy.