Do Cathedral Windows Flow In Human Time Scales?

Up to now it has been common belief that glass in windows may, even at ambient temperature, "flow" downwards over long periods of time, pulled by the force of gravity. The idea is based on reports that old stained glass windows are thicker at the bottom than at the top. In this paper the author uses basic concepts of physics to assess whether there is any truth in the theory, and comes to some surprising conclusions.