Re: (OT) Re: A89: What's Wrong?


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Re: (OT) Re: A89: What's Wrong?




I hate to post offtopic, but I hate to let incorrect posts go by even
more -- so to prevent any more myths from spreading, let me correct some of
these points:

> Glass is a solid that behaves like a liquid.  I don't know if that's what
> TGaArdvark means or not but, I think it is.  It's why, if you see some old
> glass, it'll be thicker at the bottom of the pane and thiner towards the
> top.

No, the original poster -- who stated that glass is an amorphous liquid --
was correct.

A solid, by definition, consists of a rigid, crystalized unit -- it has a
clear structure that is repeated over and over again throughout the
substance.

Glass, on the other hand, is not crystalized, and, in fact, is not a solid -
it's a liquid.  More specifically, it's an "amorphous" liquid: one that
appears solid and that does not _appear_ to flow.  Since it does not have
the rigid crystal structure, glass _will_ flow -- but this process takes
_millions_ of years.  See more below:

> > that the stained glass windows of some medieval churches seem to
> > "run"...
>
> I believe that's so...  But, I'm not positive.  I'm near positive.  I hope
> my extremely limited knowledge helped you out in some form or fashion...

According to my (up-to-date) chemistry book, glass _will_, flow; _however_,
this will take millions of years.  No man-made glass has been around long
enough to exhibit any _noticeable_ change in appearance.  Rather, as another
poster already stated, the reason that medieval glass windows are thicker at
the bottom is much simpler: due to imperfections in the glass-making
process, medieval glass was typically thicker on the bottom than on the top.
The builders, exhibiting common sense, put the thicker end on the bottom.
Thus, although the glass may appear thicker on the bottom today, that's
exactly how they saw it hundreds of years ago when the glass was created.

Since the myth that this thickness is caused by flow is so widespread, I
wouldn't take any of this on any one person's authority -- just go find a
modern chemistry book, search the index for amorphous, and you'll probably
find something very similar to the above paragraph nearby.

    -Scott




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