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From: marty@puppsr5.Princeton.EDU (Marty Ryba)
Newsgroups: sci.space
Subject: Re: orbiting bodies
Message-ID: <3972@idunno.Princeton.EDU>
Date: 9 Nov 90 19:57:32 GMT
References: <1516.27389CA9@ofa123.fidonet.org> <1990Nov9.083328@ecn.purdue.edu>
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In article <1990Nov9.083328@ecn.purdue.edu>, cyliax@ecn.purdue.edu (Ingo Cyliax) writes:
|> So is it common for moons to have the same axial rotational period
|> as the orbital period, so that only one side is visibilty from the
|> planet. If it is, what are the reasons for that ?

Well, a rather technical reference is Alexander, M. E. 1973, "Astrophysics and
Space Science," v. 23, p. 459.  He numerically models close binary systems
and specifically the Earth-Moon system computing the time scales for
synchronization of rotation and circularization of the orbit by tidal forces.

A short and more readable paper is Press, Wiita and Smarr, 1975, "Ap. J.
(Letters)," v. 202, p. L135.  They concentrate on how to get strong viscosities
in close binaries (stars), but give more readable formulae for tidal locking
timescales.  Eventually the Earth's rotation will be slowed to match the
moon's.  Tides dissipate rotational energy.  Anyone with a rough number for
the earth's mean viscosity???
-- 
Marty Ryba                      | slave physics grad student
Princeton University            | They don't care if I exist,
Pulsars   Unlimited             | let alone what my opinions are!
marty@pulsar.princeton.edu      | Asbestos gloves always on when reading mail