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(I was away from the computer for a few hours.)

Thanks for the great links. This is fascinating stuff.

The excerpt you posted makes clear how complicated orbital interactions can be.

Besides the moon, other influences.
"the gravitational pull of the other planets in the solar system, especially the giants Jupiter and Saturn, causes a different kind of precession: a wobble in the plane of Earth's orbit. "

If Earth could go through 85 degrees of change in tilt on a periodic way, climate and geology here would be greatly affected.

Here are just a few of the periodic motions/oscillations of the earth and its orbit. :-)

The Earth is tilted on its axis from the plane of the ecliptic by 23.5 degrees. That tilt causes the North Pole to be currently pointed towards Polaris. As the Earth moves around the sun its pole stays pointed at Polaris. This is the cause of the seasons we experience. Note. This tilt varies back and forth from 21.6 degrees to 24.5 degrees approximately every 41,000 years.

There is also a precession of our pole and it sweeps a complete circle in the sky about every 26,000 years. This gives us different pole stars as the north pole of the Earth sweeps out a circle on the celestial sphere.

There are also a number of other motions that must be taken into consideration over the years such as the precession of the aphelion. Our Earth’s orbit around the Sun is not a perfect circle. It is an ellipse with the closest point of the orbit called the perihelion and the furthest point the aphelion. Currently the aphelion falls on the fourth of July. However, this is not always the case. The aphelion and perihelion change over the centuries and sweeps thru the calendar year with a periodicity of around 22,000 years.

The Earth’s eccentricity is very small. However, even this changes over time. Its eccentricity varies periodically about every 100,000 years.

There are also other motions caused by the Moon, Jupiter and the Sun called Nutations. One of the major nutations has a period of 18.6 years.