Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Nutation



Regarding Chuck's comment:

Careful there Jim.
It is a question that might constitute 'trolling' for the 'tide'
thing.

If you have an explanation that does NOT include the nasty 'tidal
bulge' - please share it with the rest of us.

Actually, the precession and nutation of the Earth's spin axis is
completely unrelated to its very tiny tidal bulge. What drives it
is the torque exerted on the Earth by the unbalanced coupling
between the gravitations of the Sun & Moon differentially acting
across opposite sides of the Earth's tilted *equatorial* bulge.
The equatorial bulge (and the Earth's consequent oblate shape) is
a centrifugal effect due to the Earth's spin (and is *not* a tidal
effect). This torque tries to straighten out the tilted spin
axis, but only succeeds in precessing it because of the large
prior nonzero value of the Earth's spin angular momentum along
that axis.

David Bowman