Re: Planet rotation

[Ron Ebert <ebert@CITRUS.UCR.EDU>]

At 11:41 AM 7/7/99 -0400, Jim Braunsdorf wrote:
> I was reading a couple of recent notes and started wondering about
planetary rotations.
>      Is it possible for a planet not to rotate?
>
> I believe from a dim recollection of past readings that planet rotation is a
> residual effect of the accretion of particles that formed the planet bringing
> momentum through collisions.  I know it can be affected by tidal forces.
> Can it be zero? Why or why not?

Planets were formed by the accretion of matter from the pre-solar disk that
surrounded the protosun. In order for a planet to end up with no rotation,
the net angular momentum of all of the constitute particles that
contributed to its condensation would have to add up to zero. This is
possible but not very likely. And as others have indicated, once planets
form they interact with other bodies like the sun and their moons through
tidal forces that can alter a planet's rotation.


Ron Ebert
ron.ebert@ucr.edu
"""""""""""""""""""
Scientific theories are the BEST things we have to describe the world. If
something is "just a theory" it may not be perfect but it is just about as
good as it can be! - Bill Arnett, Astro List