Re: Planet rotation

[Leigh Palmer <palmer@SFU.CA>]

> Regarding Chuck Britton's question:
>
> > If indeed, as it appears, Venus has retrograde rotation, won't the
> > sun's tidal effect be to STOP its rotation (relative to the 'fixed'
> > stars) and then move it toward the non-retrogade rotation that will
> > match its year?
>
> That is the direction of the change the Sun's tidal effect would have on
> the rotation of Venus, but *I think* that there is not enough time
> available for the synchronization to occur since long before this time
> the Sun is expected to eat Venus when it swells out as a red giant in
> about 5 billion years (as I recall).
>
> David Bowman
> dbowman@georgetowncollege.edu

David is correct, but the time for this interaction to complete the
locking process is not readily calculable. I've been working on the
interesting problem of Neptune and Triton without much success. The
process approaches completion asymptotically anyway, since in the
end the relative motion will be nutation about the lock with ever
diminishing amplitude. I should also mention that another tendency
of such two body tidal interactions is circularization of the orbit.

Leigh