dipper@utastro.UUCP (Debbie Byrd) (01/30/86)
There's no real "earthrise," as seen from the moon. We'll tell you why not, after this. January 30 Earthrise Earthrise seen from the moon. Sounds beautiful, doesn't it? But the fact is that there is no earthrise seen from the moon. It just doesn't happen. From the side of the moon that faces Earth, our planet hangs nearly motionless in the lunar sky. It doesn't come up, or go down -- no earthrise, and no earthset either, for that matter. On Earth, things rise and set because Earth rotates on its axis once every 24 hours. The moon also rotates. But it completes a single spin in 27 days -- the same amount of time it takes to complete one orbit around the Earth. The result is that we always see the same face of the moon -- the nearside. The farside of the moon was seen by earthlings only since the dawn of the space age. Likewise, any beings on the farside of the moon would never see the Earth. Earth never appears in the sky from that side of the moon. From the moon's nearside, you'd see the Earth in a particular place in your sky -- a place that wouldn't change -- or at least not enough to notice. Again, it wouldn't change because that side of the moon is permanently locked toward the Earth. So you'd never see an earthrise from the moon. But you'd see the Earth change its phase -- from a crescent Earth to full and back again -- all taking place before your eyes over the course of about a month -- as the moon moves in orbit around Earth. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin
gsmith@brahms.BERKELEY.EDU (Gene Ward Smith) (01/30/86)
In article <325@utastro.UUCP> dipper@utastro.UUCP (Debbie Byrd) writes: >There's no real "earthrise," as seen from the moon. We'll tell you why >not, after this. Gimme a break, huh? Ever heard of lunar libration? > ucbvax!brahms!gsmith Gene Ward Smith/UCB Math Dept/Berkeley CA 94720 ucbvax!weyl!gsmith
chris@umcp-cs.UUCP (Chris Torek) (01/31/86)
> So you'd never see an earthrise from the moon.
Actually, if you travel over the moon's surface, you can generate
your own Earthrise. And believe me, it is quite a sight :-).
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1415)
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