In a message dated 11/27/99 7:22:41 PM Pacific Standard Time, firstname.lastname@example.org writes:
> > Sean Stickle wrote:
> > > Read Mach, the explanation is quite clear. There are no preferred
> > > frames, therefore any point in space can be considered the center.
> > Not with rotation. Rotating frames aren't inertial.
> Btw, the earth does not rotate around the sun any more than the
> sun rotates around the earth; they rotate around a common point
> between them (if we bracket the gravitational effects of the other
> planets) - this point is much closer to the sun than it is to the earth
> due to the "massive" disparity in mass between them.
The original post (long since lost) said to ignore that quibble. The argument is over whether "the sun rotates around the earth" is just as true as "the earth rotates around the sun". Technically, as you point out, both rotate around a common mass, but to quibble back, that point is actually inside the sun.
In any case there is a center of rotation; wherever it is, the claim "the sun/earth do not go around that point" would be wrong.