Glass viscosity calculations debunk the myth of flow in medieval windows (2017)
Finally! I always knew my 7th grade science teacher was full of shit on that one, she was so adamant about some things that turned out to be wrong.
This one was maybe more excusable because it was common to teach at the time. Maybe it ended up making us better students in the end because we learned to fact-check our teachers, and not to be adamant about things we only think are true (though I'm still guilty of that myself sometimes)...
Wikipedia - List of Common Misconceptions
Yeah, I learned this "fact" in school as well. Later I found a simple refutation: If a church window pane would deform by a measurable amount in 1000 years (say 0.5mm), then a 100-year old telescope or camera lens would be totally useless, and yet they seem to function all right.
I wonder if the craftsmen also knew that the windows were a little wedge shaped from manufacture and put the thick bit at the bottom. That's what I'd do at least, makes sense structurally.
Then later, random people made guesses as to the 'flow' of glass because all the windows are thick on the bottom...
If anyone can confirm this theory, you and I will feel eternally smug. Best of luck!
but tarmac does flow at an observable rate, although only observable over the course of years
While this was specifically about glass from the middle ages, is there certain window glass more recently that does flow measurably? The soda lime glass referenced?
Or when you see waves in window glass in 1930s buildings, is that too from the original imperfections in the glass fabrication itself?
>Their measurements reveal that medieval glass has a much lower viscosity than expected at room temperature—16 orders of magnitude less than previous estimates
It's pretty rare to read an article in which the degree of previous error is sixteen orders of magnitude.
How does this viscosity compare to gold or silver? Those also have brownian motion under the force of gravity.
I bet it’s higher than 1 nm / billion years.
Well, glass is still a liquid, which was the most counter intuitive claim to me, whether or not the flow is humanly perceptible. In fact it is even more counter intuitive now, since glass is an even more solid liquid.