Is it a myth that the stained glass in older European cathedrals has “flowed” slightly out of its original shape? The beauty of this story is the soft lead framing which would compensate to some degree for thickening at the bottom of each pane.
Arnold:
In your cite the guy is hedging. he says for all practical purposes that glass is a solid, and then does that “eye of the beholder.” This is total Boooshwaa as there is no beholder or perspective from which glass flows.
A fluid, by definition flows. Glass does not.
It’s fluid like in that its structure does not change from when it is a true fluid to when it is a solid, but a fluid is not defined by structure, it is defined by flow.
The problem is that our concepts of fluid, solid, gas, are just that, concepts, or maybe tendencies. They are useful concepts, like any good generalization, but reality is a little more complex.
By any rational way of thinking, glass is a solid.
I think Cecil knows this which is why he was hedging so much in that final part.
Tree:
The glass is thicker in medieval windows because of the manufacturing method. That’s all.
Oh, and the guy that screwed everything up and got people thinking that glass was a liquid was a german physicist who studied glass as a thermodynamic system back in the 1800s.
This is Gustav Tamman (Figures this would be the German’s fault)
He was misquoted in translation as saying “Glass is a supercooled (undercooled) liquid.”
What he actually wrote was “Glass is a frozen supercooled liquid.”
The mistranslation stuck.
And, finally the ASTM standard for determining whether a material is a liquid or a solid is as follows:
Now seeing as it takes 10 billion years or so for glass to flow by 4 or 5 angstroms, it would take…
Well, even my Scientific calculator can’t go that high.
How about we just call it a million billion gazilion years for glass to flow the 2 inches required by the test.
Since this is somewhat longer than three minutes, glass is a solid
One of the scientific definitions of the terms solid and liquid involves phase transitions. Solid and liquid are phases of matter which are exhibited by some materials (not including glass). When a material makes a transition between two phases (at a constant temperature and pressure) the material will take in (or put out) heat without changing its temperature until the entire quantity of the material has changed phase.
For example, ice melts at 32 °F (0 °C). The mixture of ice and water will remain at that temperature until it’s all melted.
Glass undergoes a transition between the hard brittle form that we make windows and utensils out of to the gooey form that glassblowers can shape into cute ornaments, to the even gooeyer form that glass manufacturers can pour into flat panes. The transition is called (surprise) a glass transition and the rate at which the temperature changes as the transition takes place slows down but does not stop.
A glass (meaning anything that exhibits glass transitions rather than phase transitions) which is in or maybe close to the temperature range of its glass transition will definitely tend to sag. The glass transition for window glass is way higher than anything normally encountered in the environment.
As Jared pointed out, Cecil’s original answer was incorrect. The frequency dependence of a substance’s electromagnetic response has nothing to do with whether it is liquid or not.
Chava
Didn’t Marilyn vos Savant also contribute to the “glass is a liquid” lore in one of her columns?
Bad example. Silly Putty shatters.
Silly Putty is a solid.
How do you get Silly Putty to shatter? I read this recently, so I hit a ball with a hammer. The hammer just bounced back at me. Does anyone know what it takes to get Silly Putty to shatter?
Put it in the freezer for an hour or two and then whack it with the hammer.
psychonaut - simple observation: the equipment used to hold the pitch so it can flow? It’s glass. I think that should clearly show the rate of flow is much lower, no?
Alright, I’m sick of this discussion (although, I note, I’m in the “glass-is-a-solid” camp).
You’ve all got it WRONG
Glass is a REALLY supercooled GAS!
If you let it sit around long enough it diffuses throughout the room. It’s just that nobody has done the experiment long enough.
That should be the ideal compromise – a solution that’s equally unacceptable to everyone.
This discussion has gone on in this forum a number of times previously. Please refer to:
among others discovered by search. Please also note that not only has Unca Cece dealt with this question, but so did SDSTAFF member David; the last thread referenced above dealt with HIS attempt to answer the question.
Good cites. Note that it was me that found Gustav, and the standards though.
But what constitutes a mixture? There are icebergs in the North Atlantic, but the water temperature isn’t uniformly 0°C.
Striations are caused by the windows being made by squeezing the molten glass with rollers. Uneven pressure caused the striations.
Hi it’s me, Shane (spelling intact).
Wow, I haven’t been here in a long time! Most of you will not remember I was ever here.
I think the only way we will ever conclude this (given that Cecil is the smartest man alive) is if he makes a personal appearance in this thread. Oh Yea, and David needs to show up too because they are both emphatic about thier opposite stances. That is the only way…might as well not even discuss it!
However, the thing that bothers (or worries) me the most is not the answer to the question, but rather the manipulation of my original question. While most of it is intact, he failed to point out that in my original question I pointed out David’s response to the question “why does glass slide” or something like that, and wanted to incite a battle royale. Afterall that’s more fun than the original question isn’t it? Not only has the most recent version that has showed up changed from my original question…the question and answer is altered from the version he actually printed a few years ago. That’s two manipulations…who knows what I really asked now? Mabye I asked why the ice in my glass always falls out when I’m melting from the acid hit?:o
It’s understandable that he has editing rights to increase sales, but it’s just not fair to hide the previous conclusions from new readers. Why is he still printing the glass is liquid answer when David is still saying it’s not.
And I never made it to speak with Regis. For my ego, anyone remember me?
A), No, Silly Putty is demonstrably a liquid.
B), It shatters at room temperature if you hit it hard enough (unless they’ve changed the formulation since I was a kid).
C), jmacleod9975 is correct. The whole liquid/solid question is immaterial, having nothing to do with transparency one way or the other.
Then, by all means, please demonstrate it.