8:07 PM EDT today, March 20, marks the Vernal Equinox and the official start of Spring 2007.  Today at that time the sun will pass over the equator from the southern hemisphere to the northern.   This is what you probably already know.

But I learned a couple of things today that I didn't know.  First is that “equinox” means “equal night”, which makes sense because on the equinoxes the length of day and night are exactly equal.  Here in the northern hemisphere the days will continue to get longer until the Summer Solstice at 12:06 PM EDT on June 21, 2007.  Since the last Autumnal Equinox we in the northern hemisphere have been getting less direct light than the southern hemisphere.  As of 8:07 we will officially begin receiving more direct light than the southern hemisphere.

The other thing I should have known is that, for the southern hemisphere, this time will mark the Autumnal Equinox.  I mean, I was aware that the seasons of the south are the reverse of the seasons of the north, winter here summer there, fall here spring there, but it just never occurred to me that the solstices and equinoxes were similarly flipped.  Silly that should never have occurred to me.

Oh, one other little thing I learned is that “solstice” means “sun stands still”.  Since the solstice marks when the sun stops moving north or south and reverses direction, that's a very sensible thing to call it.

Another interesting tidbit, apparently the great Sphinx of Egypt is oriented so that it exactly faces the sunrise on the morning of the Vernal Equinox.