RicodJour wrote:
On Dec 10, 6:50 am, Phisherman wrote:

Most glass is a liquid and sags. In an old house you may see the
bottom of the windowpane is thicker than the top portion. Quartz
glass is a solid--probably less sag over time and transmits more
lightwaves than regular glass.

I believed that for a long time until it was pointed out to me that
there are intact glass windows in Roman and Egyptian buildings which
would belie the flowing glass myth. If the glass sagged enough to be
noticeable in a two hundred year old house, the sag in two or four
thousand year old glass would be very noticeable, and it's simply not.

http://www.glassnotes.com/WindowPanes.html

http://dwb4.unl.edu/Chem/CHEM869A/CH...en/florin.html

R

I've seen lots of old, wavy glass - new wavy glass too, especially in
China - but have always attributed that to lousy glass making. Never seen
any thicker at the bottom though.

There appears to be no argument about glass being an amorphous
(non-crystalline) material. When I was a geology student more than 50 years
ago we were taught that there is no such thing as glass beyond a certain age
(some multi-millions of years) because it ultimately crystallizes. Now,
humans haven't been making glass long enough for it to crystallize but there
are naturally occuring glasses - obsidian, for example - and it was/is those
that were not found beyond a certain period in the past.

OTOH, the profs all po-pooed poor old Alfred Wegener and his silly
continental drift idea

--

dadiOH
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