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Re: moon's synchronism



At 07:54 PM 3/23/98 -0800, you wrote:
Now that I think about it some more the sun ought to produce a torque
affecting the moon's orbital angular momentum which should cause its orbital
axis to precess around a line perpendicular to the earth's orbit. I have no
idea of the period of that precession.

That's correct. The period is about 18.6 years. The inclination
is appreciable, about five degrees, and the effect is to make the
motion of the Moon as observed from Earth a bit difficult to
predict by mental calculation. Another torque acting on the Moon's
orbit is due to the quadrupole moment of the Earth.

Leigh

I should have remembered that. I think I remember that studies of
Stonehenge indicated that the "Aubrey Holes" were intended to keep track of
this period to predict solar eclipses.
Jim Riley
Department of Physics
Drury College
Springfield Missouri 65802
(417) 873 7233
e-mail: jriley@lib.drury.edu
fax: (417) 873 7432