> do we account for window glass that has become thicker at the
> bottom of the pane than at the top?  Apparently glass 'flows' over time -
> years not weeks - and window panes change shape!
> Nigel
> British Library

Well Nigel, according to the old wives and those who might decline to
check the website of the Corning Glass Museum, this can't occur!

The stuff has long been regarded as a very slowly
flowing liquid that is moderately elastic at temperatures normally
considered to be tolerable to we humans, and other similarly consituted

As for 2000 year old bottles apparently not having changed shape
since they were blown, how can anyone possibly know this?

Assuming that an ancient metal mould might have survived and not have
changed shape
(I wonder if any glass vessels were moulded as such in antiquity), and that
object molded from it could be measured (accounting for shrinkage due to
proving that it could not occur would be quite a challenge.

Perhaps with the exception of something that's been sealed hermetically,
(even that's possibly not an assurance of precluding physical changes of
solids) it is
highly questionable to  ASSUME that any old substance is in precisely the
condition as it was when created by any means, natural, man made, or
otherwise (whatever that might be!)