To our short life span, the desert seems eternal, but science shows us otherwise. But surely we can depend on night following day. Well, yes, but that night and day hasn't always been like today's. Think time flies? You should have been around millions of years ago! By one set of estimates, the day was only a little over 21 hours long a mere 500,000,000 years ago, and today, of course, stretches out to 24 hours. What's going on?
It's lunacy, of course. No, not craziness, the moon! The tides
caused by her act as a brake, slowing earth's rate of spinning. Physics tells us
this much, but how did we figure out how many days in a year, looking back millions of
years? Corals and other sea creatures to the rescue. Some of these animals add daily to
their skeletons and, at the same time, preserve an annual record, leading to the
estimates we're talking about. Easy? No, and perhaps our estimates aren't
highly accurate yet. But we'll improve—after all, we have plenty of time.
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.