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Desert Diary
Physics/Moon Size


A full moon rising above the horizon seems huge—a sight lovers can easily assume was made just for them. But think how much more dramatic a moon twice the size would be. Impossible? Right now, sure, but the moon wasn't always where it is now. Seems like our little sister, as she ages, is growing more and more distant. Isn't that just like a kid? But to add insult, she's doing it by "borrowing" from us.

As we do our little dance in space, some of earth's rotational energy is transferred to the moon, causing it to move faster and thus slowly edge away. In fact, space-age measurements indicate that the moon moves about 1.5 inches farther away every year. And earth's loss of energy equals about 6 days since the dinosaurs disappeared, going from about 371 days to our current 365. If you'd been in our Chihuahuan Desert a mere couple of billion years ago, if there had been a Chihuahuan Desert, which there wasn't, that beautiful orb would have been twice as big.
pen and ink


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.


Our increasingly distant satellite. Image courtesy of NASA.