All
First, in reply to Eric's query. I'm a geophysicist, so no more qualified
than he in this area. But I guess you don't need to be qualified to ask
questions, just to answer them.
Anyway, not having given this rotation effect topic any thought before
this, it seems to be getting interesting, so here are some more unqualified
thoughts. The forces James described in his recent email are not the only
ones acting on a rotating body. If you change the mass distribution by
moving mass nearer to or further from the axis of rotation, you change the
moment of inertia, and this affects angular velocity (try sitting in your
swivel chair and giving it a spin with legs extended, then retract).
Convection current certainly move mass up and down, so there are some
rotation-linked forces. In a complex system like the Earth, made up of
concentric shells of very different rheology, I would expect these to
promote shear and differential rotations. However, not being a
geodynamicist, I have no idea how large these forces would be. Intuitively,
since the rate of mass transfer is pretty small, I would expect them to be
several orders of magnitude too small to have any effect. But that is only
an uneducated guess. I can't believe that no-one has looked at this,
perhaps back as far as when they were rubbishing Wegener. Anyone got the
authoritative answer?
John Milsom
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