Glass is not a liquid!

[PowerMacX]

I tested my program on a Radeon X1600 mobility today (Macbook Pro). It ran 10x slower than on my X1900XT (Mac Pro) :cry:

I can test it on my Macbook (non-Pro) if you want... [insert evil laughter here]

I guess it would turn into a very realistic simulation of glass... after all, glass is a liquid, right? It justs flows really, really slowly... :p

[kelvin]

I can test it on my Macbook (non-Pro) if you want... [insert evil laughter here]

I guess it would turn into a very realistic simulation of glass... after all, glass is a liquid, right? It justs flows really, really slowly... :p
No, actually, glass is not a liquid and does not flow (http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/florin.html#say).

[/fact troll]

[PowerMacX]

No, actually, glass is not a liquid and does not flow (http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/florin.html#say).

[/fact troll]

Oh, C'mon! :) From that very same link:
[...] glasses are frozen-in non-equilibrium systems.
As kinetically frozen forms of liquid, glasses are characterized by a complete lack of long-range crystalline order and are the most structurally disordered types of solid known.

And from Wikipedia (yes, I carefully selected this single sentence, please do not read the rest of the entry ;) ):
Writing in the American Journal of Physics,[9] physicist Edgar D. Zanotto states "...the predicted relaxation time for GeO2 at room temperature is 10^32 years.

So, basically it's not just "really really slow" as I said but "ridiculously slow". :sneaky:

[/ridiculously off-topic]

[DoG]

You can actually see glass flow. Windows of old industrial buildings, for example, tend to have a bulge on the bottom edge, from the glass slowly flowing downwards.

Of course, you have to consider that there are many kinds of glass, and only some of them deform visibly during a human lifetime :)

[maximile]

I read (I think in New Scientist) that that was a myth too - the "bulge" is formed as part of the way they shape the glass, and when it's cool and solid they installed it with the bulge at the bottom. "for the sake of stability and visual sparkle", according to Wikipedia.

[backslash]

According to The Physics Factbook™ (Edited by Glenn Elert -- Written by his students) glass is a liquid... at temperatures above 1425-1600 °C (depending on composition). I pretty sure the average window is not that hot though.
:p

[DoG]

I think some glasses do deform over time, especially some old mixtures containing lead.

Actually, if you think of it, there's no clear boundary between amorphous solids and liquids, as there isn't really a phase change. Things just slow down a lot :)

IIRC, an important difference was that crystalline solids deform much more slowly under continuous stress than amorphous solids, due to the crystal boundaries acting as barriers. Either way, fun stuff :D

[AnotherJake]

It seems like every chemistry instructor I've ever had liked to point out that glass is an amorphous solid and can deform over time. I personally have seen glass that had clearly (no pun intended) , but slightly, molded itself into/onto the bottom of a window frame (not just thicker, but melted) -- even molded grains of sand into itself from the pressure in that spot too. I have seen sites on the internet who say it simply ain't so, and they are mistaken. And if you still don't believe me, oh well. Some day you might see it too and will recognize right away that it darn-well it wasn't made like that.

[aarku]

There's no "belief" involved, here.

Seems like an easy enough experiment to set up. Procure a longish thin glass tube/rod and affix one end to a support, letting the other end sag with gravity. Measure the deflection over time. Keep it at a reasonable temperature range. It either changes (flows) or doesn't.

Surely someone has done that.

-Jon

[maximile]

There's no "belief" involved, here.

Seems like an easy enough experiment to set up. Procure a longish thin glass tube/rod and affix one end to a support, letting the other end sag with gravity. Measure the deflection over time. Keep it at a reasonable temperature range. It either changes (flows) or doesn't.

Surely someone has done that.

-Jon

Hehe... nice idea. From wikipdeia again:

A myth does exist that glass rods and tubes can bend under their own weight over time. To test this, in the 1920s, Robert John Rayleigh, son of the Nobel Prize winner John William Rayleigh, conducted an experiment on a 1 metre (~39 in) long, 5 millimetre (~3/16 in) thick glass rod, which was supported horizontally on two pins with a 300 gram (~0.66 lb) weight in the middle. Apart from the initial bending of 28 millimetre (~1.1 in), the position of the weight did not change until the end of the experiment, which lasted for 7 years. At the same time, another man, a worker of General Electric named K. D. Spenser, conducted a similar experiment independently. Two months after Rayleigh, he published his own results which also disproved the myth. Spenser suggested that the myth was composed before the 1920s, when the tubes were made by hand, and naturally some of them were curved to begin with. Over time the straight tubes were taken away, and only the curved ones remained. Some people probably thought it was the glass flowing.

[AnotherJake]

It seems like there is a never-ending supply of debate over it. Sounds almost like whether or not UFOs exist.

On that experiment: Only seven years? Only one type of glass?

[PowerMacX]

Someone submit this to Mythbusters!

[aarku]

On that experiment: Only seven years? Only one type of glass?Are you saying you hypothesize that after a certain amount of time only does the glass begin to flow? Otherwise, if your measurements are accurate enough you should be able to measure even a slight change in deflection after 7 years if it is truely visibly noticeable after 100.

And I have no idea with regards to different types of glass. I'm sure there are oodles.

This doesn't seem to be MythBusters friendly because it's not very visual, unless they weigh the glass down with high powered explosives, and it is too long an experiment.

-Jon

[AnotherJake]

Are you saying you hypothesize that after a certain amount of time only does the glass begin to flow?
No, not at all! I am merely suggesting that the experiment may be flawed. I have no idea what caused the glass I saw to deform into the shape of its frame (except that I remembered some of my chemistry profs pointing out that it would, so I didn't think much of it), but I do know it was a hell of a lot older than 7 years! At least sixty.

What about heat? What about cold? Humidity? Other chemicals? How about mechanical disturbances and prolonged vibrations from the structure or the wind? How about UV? There are just so many variables to take into consideration, and over such a long period of time, that I don't think it would ever be possible to prove or disprove it using a simple experiment. One would need a sample. So I guess looking at it in that light, until someone can produce a sample proving that it can indeed deform in its solid state, we'll just have to assume that it can't -- except *I* know that it can, but that's irrelevent to you because I can't prove it without the sample now can I... Why does this remind me of iocane powder? Certainly, had I known at the time that this would have been such a big deal many years down the road, I would have kept the one I saw, and will most definitely keep the next one! :)