[evaneykelen]

I lived in a house built around 1605 in the Netherlands, with some of the windows being hundreds of years old, based on expert opinion. The glass had started to droop downward in certain places, almost like the resin you see in trees. It made me realize that glass is not as rigid as I thought.

[scheme271]

I think that glass flowing thing is a myth. The manufacturing method back then resulted in uneven panes and they were installed with the thicker side at the bottom.

[mjevans]

I'm not entirely convinced it is a myth, but the practical effect surely is.

I do suspect that over insanely long periods an otherwise undisturbed physical object would flow-sag at some rate under the influence of a constant force in a given direction.

No idea how long that would take, but erosion and other destructive forces appear to dominate so for practical measures any such effect is likely against the noise floor.