Re: mass extinctions and DDT

[Graydon <graydon@dsl.ca>]

On Sun, Dec 30, 2001 at 09:27:49AM -0500, Jordan Mallon scripsit:
> >From: Daniel Bensen <dbensen@gotnet.net>
> >Aren't there some big windows in a chaple in Europe that are now >thicker 
> >at the base because glass is just a really really viscous >liquid?  Or is 
> >that science babble?
> 
> Well, I'm not overly sure about the window thing, but I can say with 
> certainly that glass is an >extremely< viscous substance.  Not likely to 
> see it flow on its own in our lifetime.

There are, indeed, church windows where the glass is thicker at the
bottom than the top.  Since there are also windows of similar age where
the glass is thicker at the top than the bottom, and windows where the
thickness of the glass has no discernible vertical orientation, it's
regarded as most parsimonious to consider the variations in glass
thickness as a function of the available manufacturing techniques, which
could not produce glass of consistent thickness, rather than in-situ
changes due to behaviour under gravitational stress over time.

Which is a good thing, or enormous obsidian cliffs would ooze and slump
and spread over the landscape like slow sea waves over geological time.

-- 
graydon@dsl.ca   |  Hige sceal þe heardra, heorte þe cenre,
                 |  mod sceal þe mare þe ure maegen lytlað.
                 |   -- Beorhtwold, "The Battle of Maldon"