Re: [Phys-l] Clarification: A ball at the center of a planet - retract

[brian whatcott <betwys1@sbcglobal.net>]

 When dealing with angels dancing on pin heads, it is fair to 
accentuate the positive,
 no doubt - but not to ..er.. lie.
Fortunately, the august readership of this list passes lightly over my 
modest
 contributions without much cerebration. Here, I seem to have passed on a
 factoid worthy of Snopes: that rubber shrinks on heating.

Well, yes it does, sort of.  You have undoubtedly heard popular accounts 
of fan belts
shrieking when cold,  going silent when warm?  Like that.    Now there 
certainly ARE
materials with negative thermal coefficients of expansivity over some 
small even
 wide temperature range, but you won't find rubber with a negative symbol
 in the list (at least I didn't)
 But wait a moment, didn't you hear of elastic bands shrinking when 
heated?
Probably.
But the  issue tends to become the anisotropic coefficients of a long chain
 molecule that offers more of less untidy folding with temperature.

Sorry about that

Brian W

On 10/4/2010 8:50 PM, brian whatcott wrote:
>    I see merit in Brian's question: as I note (again and again);  ignoring
> radioactive heating (which  occurs in most conceivable planetary bodies,)
>    leads one to Thomsonian error.
> So  the radiative heating would have its affect on the rubber ball,
> after some equilibrating time period.
> Rubber has the curious property of contracting when heated
> which would be the dominating effect in this situation.
>
> Unless it were spinning, I suppose?      :-)
>
> Brian W
>
> ***
>
> On 10/4/2010 1:11 PM, Crawford MacCallum wrote:
> > I think there is no force on any particle anywhere in the
> > cavity, so (C).
> > Crawford
> >
> > On Mon, 4 Oct 2010 14:04:45 -0400
> >     "Brian D. Shock"<Brian.Shock@powhatan.k12.va.us>   wrote:
> > > Sounds like the net force acting on the ball before and
> > > after is zero, so no change in the r. Is there a
> > > temperature change?
> > >
> > > Brian Shock