Re: moon's synchronism

[Leigh Palmer <palmer@sfu.ca>]

> 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