Friday, March 20, 2009

The Astronomical Spring

As I write this blog, the spring equinox is occurring across the Northern Hemisphere, the half way point between the winter solstice and summer solstice; the latter two events occur when, due to the tilt of the Earth's axis, our Hemisphere leans most away from or most toward the sun, respectively. By definition, spring stretches from the spring equinox to the summer solstice, making this the first day of that beloved season.

Falling on or about March 21, the spring equinox provides no guarantee that winter is over in our Hemisphere. While periods of warm weather usually precede the equinox, periods of cold weather are just as likely to follow it; indeed, the last freeze across most of North America's Temperate Zone generally occurs well into April.

But, after a long winter, it's always reassuring to know that we're now on the warmer side of nature's cycle and that the days will continue to lengthen for the next three months. We are, after all, tropical creatures.