MicroFactzzz#0122 · 🧠 Science WTF
Old church windows aren't thicker at the bottom because glass "flows" over centuries
The popular myth of flowing glass actually comes from an old manufacturing technique, not the material being liquid on a human timescale.
There's a popular belief that glass is really just an extremely viscous liquid that slowly "flows" downward over centuries under gravity — with old medieval window panes, thicker at the bottom than the top, offered up as proof.
In reality, structural analysis shows that glass at room temperature behaves like an amorphous solid — its viscosity is so enormous that any noticeable "flow" would take vastly longer than the age of the universe.
The real explanation for those old windows is much more mundane: old glassmaking techniques, using blown and spun glass, produced panes of uneven thickness, and glaziers simply installed them with the thicker edge at the bottom for stability.
Despite being thoroughly debunked, the "flowing glass" myth remains one of the most repeated "science facts" out there — a good example of how an intuitive-sounding explanation can crowd out a far less dramatic but true story.
Sources
- General knowledge / encyclopedic sources
This fact is based on generally available knowledge, not a single, citable source. See how we approach verification.
Krulicza Nora
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