[Random] Old cathedral windows being thicker at the bottom does not mean glass is secretly a liquid

[Freddie_47]

A popular myth claims that centuries old church windows appear thicker at the bottom because glass is technically a liquid that slowly flows downward under gravity over hundreds of years. It's a compelling story, but it's not true. Glass is properly classified as an amorphous solid, meaning its atoms are frozen in a disordered, jumbled arrangement similar to a liquid's structure, but locked rigidly in place rather than actually flowing. University of Wisconsin chemistry professor Mark Ediger notes that while glass technically can flow given enough time, that flow happens at a rate so slow it's essentially meaningless on any human timescale, at room temperature, a typical piece of window glass would take roughly a billion years to change shape by less than one nanometer.

The real explanation for those uneven old windows comes down to manufacturing, not physics. Medieval glassmakers often produced window panes using a spinning technique that naturally created discs of uneven thickness, and when installers cut and mounted those panes, they commonly placed the heavier, thicker edge at the bottom purely for structural stability, not because gravity had pulled it there over time.

Fact or Fiction?: Glass Is a (Supercooled) Liquidwww.scientificamerican.com