Saw this on the news...
Scientists reveal why glass is glass

I've never got a good grasp on the debate of whether glass is a liquid or a solid.
I looked for a discussion, but there's only references and not a whole discussion.
Here is mention (also per wiki) that it is an amorphous solid.

The article claims to solve exactly what it is:
Considering they reference this...
...which I always thought was an urban legend (that the glass was always imperfect and installed thick side down)
It makes me think that the article is suspect in some ways.

Any thoughts or comments?

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Numbers are not case sensitive. (me)

It is suspect - you are right. The reason older glass varies in thickness is because of how it was made back then. The Pilkington method of "float glass" yields the uniform-thickness glass.

I live near Corning so I've seen this: Glass panes originated from a large cylinder of glass that was spun flat - so you can imagine the outer endges would be thinner than the inner. hence the variance in glass thickness. That's oversimplified but it sums it up.

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---"Why do things have to suck so bad?" a friend once asked me.
"Because space is a vacuum and that's a lot of suck." I replied.
(Actual quote)---

What LotusExcelle said. And the reason that the glass in old buildings is thicker on the bottom - if you were putting a piece of glass in a window frame, how would you put it? With the thicker part down.

As far as glass being a solid or a liquid... I say it is glass, which has properties different than either a crystalline solid or a liquid. But if you have to pick, I pick solid.

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At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009

glass is referred to as "soft condensed material"
more here:

http://www.sciencedaily.com/releases...0809130014.htm

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Disclaimer: I have no theories, I am not smart enough to come up with theories. I only have a hypothesis. So anything I may write, statement or otherwise is just a hypothesis based on what I observe...

The difference between a correlation and a causation... Everyone who drinks water dies... Water makes things wet...

I pick fluid. It's not an urban legend - the panes of old windows are thicker at the bottom and I really don't think it is because they were installed that way.

Smaller panes of glass are normally cut from a larger sheet.

Geonuc - the pane thickness difference has to do with how those panes were made. Float glass didn't exist and the way they were made meant that they all have varying thickness. Go to Corning - they have some glass cylinders in various stages of making panes. And you can see the process by which this happens. Let me see if I can find a link... i'll post later.

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---"Why do things have to suck so bad?" a friend once asked me.
"Because space is a vacuum and that's a lot of suck." I replied.
(Actual quote)---

I change my vote.

http://dwb.unl.edu/Teacher/NSF/C01/C...indowpane.html

Very glad to see you researched it! And even more glad that you changed your opinion - I think we all know how often people are stubborn. Very refreshing!

__________________
---"Why do things have to suck so bad?" a friend once asked me.
"Because space is a vacuum and that's a lot of suck." I replied.
(Actual quote)---

I can be stubborn, too.

Oh me too - I think its a rather common fault.

__________________
---"Why do things have to suck so bad?" a friend once asked me.
"Because space is a vacuum and that's a lot of suck." I replied.
(Actual quote)---

I remember reading somewhere many years ago that glass actually drips every 800 years.

But let's face it, if it feels solid, even takes more than a month to drip, and it shatters if you hit it on something, then it's a solid.

If glass was not truly solid, it would make a poor material for telescope mirrors. In a telescope, even the slightest imperfection (much smaller than you could measure with a ruler) ruins the image.

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"I'm as accurate as any psychic. And I'm a cartoon!" -- Squidward

"Arrrgh, the laws of physics be a harsh mistress!" -- Bender

I'm not sure what you mean by "drips". I don't think most glasses would show any significant dimensional changes in periods of hundreds of years at any temperature close to room temperature, let alone what I think of as "drips".

There have been cases where glass has been chemically attacked, such as from sea water, and the corrosion products can form "drips" down the glass.

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At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009

Roman glass hasn't 'dripped' and there are examples of renaissance glass that haven't sagged or deformed. There is glass in Durham Cathedral that has been there for 900 years.

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'The eye can only see what the mind is prepared to accept'

There are pieces of obsidian shaped into points (by humans) that haven't changed in 16,000 years!

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(By the way, I hate it that so many papers in the areas of planetary science and geology are not easily avaiable to the dreaded "non-subscribers". It is like they are screaming at me: "YOU CAN'T HANDLE THE TRUTH". Good, I feel better now.)

I know you are a person who takes his physics seriously, but isn't it said that most great discoveries aren't discovered with "Eureka!" but with, "Hmmm, that's funny." Big Don

Lol, guess the book, or newspaper must have been wrong then. Unless they didn't mean actual 'drips', and meant sagging. Then again maybe the drips are minute?

Glass does not drip or sag or deform from age in any way over any known length of time. Heat it up and it does stuff but we're talking thousands of degrees. Any information to the contrary is incorrect entirely.

__________________
---"Why do things have to suck so bad?" a friend once asked me.
"Because space is a vacuum and that's a lot of suck." I replied.
(Actual quote)---

Curiously, substances we are quite happy considering as solid - ductile metals for example - "flow" more than window-glass does - consider lead roofing for example. But we call that "creep" and that is considered a property of solids so we are happy with that.

Pitch looks glassy, and shatters like glass when struck. But that truly is a very viscous liquid, and can be shown to drip, even when protected from the sun.

The fact that at sufficiently high pressures/temperatures, there ceases to be a phase transition between liquid and gas should remind us that phases/states can be all rather messy, and we can't expect precise classifications always to work.

Nowhere in the article did I see any mention of quartz, which, like glass is SiO₂ and, unlike glass, is a true crystalline solid.

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

It might be moderately funny if someone contacts Keck Observatory and tells them that there scope mirrors are liquid and are going to start dripping.

__________________
"I'm as accurate as any psychic. And I'm a cartoon!" -- Squidward

"Arrrgh, the laws of physics be a harsh mistress!" -- Bender

For this see the Pitch Drop Experiment of the University of Queensland.