Re: Moon's synchronism

[John Mallinckrodt <ajmallinckro@CSUPomona.Edu>]

On Tue, 17 Mar 1998, William Beaty wrote:

> The moon is still supposed to be swinging with a slight rotary
> oscillation, but I don't know if that is left over from the original
> swinging, or if it's from interaction with the sun, etc. 

Because the moon's orbit is not circular, it *can't* keep one face 
precisely oriented toward Earth at all times.  It's angular 
velocity of rotation is roughly constant while its angular 
velocity of revolution is decidedly not.

BTW, it's interesting to consider this phenomenon from a driven 
oscillator point of view.  The tidal force effectively drives the 
moon at a frequency of about 1 cycle per month.  But since that 
frequency is *way* above the resonant frequency, the moon's 
rotational inertia dominates.

John
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