Once, the movement of the sun with the seasons made little sense except as demonstrating the capriciousness of the gods. Why should the length of days change cyclically? Indeed, why should there be seasons? It wasn't until astrology was replaced by astronomy in the minds of the educated that any of this made sense. Two vital pieces of information were necessary: that the earth went around the sun rather than vice versa and that the axis of the earth is tilted such that it points in the same direction as it moves around the sun.
Currently, the north pole of that axis points toward the North Star. If
you picture the pathway of the earth around the sun as following the rim of a plate,
then the North Star is 23.5 degrees above that plate. The result? In summer, our
Chihuahuan Desert tilts that much more toward the sun and the sun is high in the sky;
and, of course, the winter sun is correspondingly lowered. So thank our tilted earth
for one spice of living: the seasons!
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.