Glass properties

No, it's an urban myth. The viscosity of glass at room temperature is far too high for any flow to occur. What happened is that the glass was installed with the thicker end at the bottom.

This question has been the subject of an academic paper:

As others have said, no, not true. The best empirical evidence is antique astronomical instruments, many of which are a couple of hundred years old or more. If glass could flow the lenses/mirrors of these instruments would have to be reground regularly, none ever do.

Marc

I think this myth is so pervasive it can be called an urban legend. As many of you know the "Glass Flows Myth" concerns the belief held by many that because glass is a "super cooled liquid" it actually has a degree of "flow" at temperatures you and I find comfortable. Those who believe this urban legend point to the fact that the windows in colonial homes and in old stained glass windows are thicker at the bottom than at the top. There was a time, in the dim dark past that, in my ignorance I believed in the myth of glass flow. What could I have been thinking? I mean doesn't it seem exciting to think that all the glass in the world is actually flowing as we speak. That the Rose Window will soon spill out of the confines of the lead cames that have held it in place all these years. Well, we can all sleep easy tonight.

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It's not so ridiculous a notion. It's true of supercooled pitch:

. . . and the experts will tell you that a combination of ever-changing weather patterns causing beach erosion, combines with melting polar ice caps, are causing the seas to rise on US beaches.

Not so!, folks.

Actually it's caused by the ever increasing weight of large collections of National Geographic magazines stored in attics and basements.

Think about it . . .

Carl Sachs

Terry Harper wrote: