# [ExI] Thermal expansion - Ball and ring experiment

Emlyn emlynoregan at gmail.com
Wed Jun 13 03:28:19 UTC 2007

```On 13/06/07, Damien Broderick <thespike at satx.rr.com> wrote:
> At 11:23 AM 6/13/2007 +0930, you wrote:
> >Yep, that's my contention also. My problem is, how to prove this to
> >someone who doesn't believe me, short of actually doing the
> >experiment?
> >
> >Emlyn
> >
> >On 13/06/07, spike <spike66 at comcast.net> wrote:
> > > The gap gets larger.  Imagine the arc piece that is missing from
> > the ring to
> > > form a C.  That piece of nothing expands the same way the piece
> > of something
> > > would have expanded were it present.  So the gap gets larger as the C is
> > > heated.
>
> Draw three concentric circles, with radii headed N, S, E and W. The
> outer annulus is what happens when you heat the inner annulus (well,
> near enough). Chop out a quadrant. The outer removed segment is
> larger than the adjacent inner deleted segment. If a gay bomb is
> dropped during the experiment, each annulus will expand even further.
>

See photo for a ship whose properties offset this additional annulus expansion:
http://cyusof.blogspot.com/2006/11/name-game.html

A bit more background...

I raised a few arguments similar to what Damien and Spike have
presented. Another was something like this...

Think of the inner circumference of the "C". If heated, all atoms move
a little further apart from each other. So the inner circumference of
the heated "C" must be longer than that of the cool "C". Similarly for
the outer circumference, etc. So, if the shape doesn't deform, ie: all
atoms stay in the same relative positions, the whole thing must just
scale up.

And that no deformation assumption was the sticking point. I assume
that it is true that the atoms are rigidly bound to each other in a
certain formation, and that's not going to change (just distances are
going to change), whereas he is thinking that they can move relative
to one another, kind of slip around, so there could be less atoms in
the inner circumference after heating, to accomodate "expanding
inward".

Now, reading from this lovely site,
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch13/category.php
it seems that the metal atoms are tightly and rigidly packed, with
electrons buzzing around wherever they like. It also seems that the
metal atoms can move fairly freely enmasse (thus the malleability of
metals).

I think, however, there is no work being done on the metal in a way
required to actually let layers of atoms slip past one another. Thus,
we can regard the atomic structure as staying put (except for
expansion). Thus I'm right.

Emlyn

```