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Re: Is Glass a Liquid?

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Il giorno venerdì 2 ottobre 2015 18:19:53 UTC+2, benj ha scritto:
> On 10/02/2015 02:55 AM, Angelo wrote:
> > Il giorno venerdì 2 ottobre 2015 07:39:05 UTC+2, pnal...@gmail.com ha scritto:
> >> On Thursday, October 1, 2015 at 8:01:39 PM UTC-7, benj wrote:
> >>
> >>> It's been known forever that most glass is just a very viscous
> >>> liquid. It's easy to prove.
> >>
> >> Not so fast...
> >>
> >> http://www.cmog.org/article/does-glass-flow
> >>
> >> http://www.scientificamerican.com/article/fact-fiction-glass-liquid/
> >>
> >> http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/florin.html
> >>
> >> http://io9.com/the-glass-is-a-liquid-myth-has-finally-been-destroyed-496190894
> >>
> >> ... every one of these sources says otherwise...
> >
> > It is hard to notice flow of glass in windows, bottles or common
> > objects.
> > A large lens in a refracting telescope offers a much more sensitive
> > probe:
> > "In very large apertures, there is also a problem of lens sagging, a result of gravity deforming glass. Since a lens can only be held in place by its edge, the center of a large lens sags due to gravity, distorting the images it produces. The largest practical lens size in a refracting telescope is around 1 meter (39 in)."
> > https://en.wikipedia.org/wiki/Refracting_telescope#Technical_considerations
> >
> > Perhaps this fact contributed in part to the abandonment of large
> > refractors (gravity deforming lenses).
> >
> > regards
> > Angelo
> 
> Note that the idiot video Wormley linked denies the above obvious result 
> and flatly states that telescope mirrors and lenses do not sag. Which 
> is, of course idiotic and false. I love the study on AMBER to prove that 
> glass does not flow! May I suggest that next time they use AMBER COLORED 
> GLASS instead.

Indeed.

And curiously BTW, our beloved electron (the particle) owes its name to 
the (ancient, classical) greek name of amber: elektron.
 
> Note that many telescope mirrors are made of special materials with near 
> zero expansion co-efficients and may or may not be non-crystalline 
> glass. To the question is not "sag" but rather are the sags permanent.
> 
> As I said, in spite of all the nonsense and misinformation and 
> misinterpretation of transparent crystalline substances as glasses, 
> glass flow is EASY to prove. I've PERSONALLY seen the proof! Where? It 
> was in the glass shop on campus. There in a corner was a bundle of glass 
> tubing that had been leaning there for God knows how many years. Each 
> tube was beautifully and permanently bent under gravity. And could not 
> be straightened out without heating or turning it the the other way and 
> waiting years. We are talking plain old soda-lime window glass here.

Perfect.
 
> Glass is a very viscous liquid. Period.

Yes, but a little more complicated: common glass is a mixture, only 
rarely a pure substance. Accordingly it has a softening range, not 
a proper melting point.
 
> The church window fallacy with the help of idiot journalists has created 
> major havoc in the story of glass viscosity. Again: The church window 
> sag is FALSE, but sagging glass is TRUE!
> 
> Here's the theory guys: Crystalline substances have bonds between the 
> atoms held by electrostatic fields (electron cloud) such that when force 
> is applied to the substance it deflects these fields which push back. 
> The force of the fields does not change over time and the bonds do not 
> break over time. The material does not flow.
> 
> Glasses on the other hand have molecules arranged in a jumble with only 
> some of the bonds of the crystalline type and the rest of lower energy 

That's true but I think that these energies are however within the same 
order of magnitude, roughly speaking.

> attractions. So the result is because of thermal statistics periodically 
> enough energy appears to shift one of those lower energy bonds. If an 
> outside force is applied at that time this will direct the shift in a 
> certain direction. Hence when enough of these low energy bonds move, the 
> object "flows" or bends permanently.

Neat explanation. Glass doesn't have a unit cell but the local 
arrangements of atoms do not differ much here and there geometrically 
or energetically. So they are enough exchangeable even at room temp *
if an external force acts upon: sort of a sliding of a pseudo-unit cell.
 
> Note that the more heat you apply the more bonds are broken and moved 

Only a little addition:
The more heat you apply the more bonds are statistically broken.

But OK

> and hence the more the material can move and the less viscous it 
> becomes. Gosh the theory actually works!

Perfect, again.
 
> You're welcome.

You are always welcome.

regards
Angelo

* Even for a strong bond there's a non zero probability of being broken 
if it can reform with only a very slight displacement, at a given temp.

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Thread

Is Glass a Liquid? Sam Wormley <swormley1@gmail.com> - 2015-10-01 19:11 -0500
  no, and yes noTthaTguY <abu.kuanysh05@gmail.com> - 2015-10-01 18:28 -0700
  Re: Is Glass a Liquid? jimp@specsol.spam.sux.com - 2015-10-02 01:19 +0000
  Re: Is Glass a Liquid? benj <nobody@gmail.com> - 2015-10-01 23:01 -0400
    Re: Is Glass a Liquid? pnalsing@gmail.com - 2015-10-01 22:38 -0700
      Re: Is Glass a Liquid? Angelo <patrizio.pan-2002@libero.it> - 2015-10-01 23:55 -0700
        Re: Is Glass a Liquid? john <johnsefton288@gmail.com> - 2015-10-02 06:33 -0700
          Re: Is Glass a Liquid? Angelo <patrizio.pan-2002@libero.it> - 2015-10-02 07:14 -0700
        Re: Is Glass a Liquid? benj <nobody@gmail.com> - 2015-10-02 12:19 -0400
          Re: Is Glass a Liquid? Mahipal <mahipal7638@gmail.com> - 2015-10-02 15:43 -0700
            Re: Is Glass a Liquid? "Le Nymster" <invalid@example.com> - 2015-10-02 19:05 -0700
          Re: Is Glass a Liquid? Angelo <patrizio.pan-2002@libero.it> - 2015-10-02 19:41 -0700
            Re: Is Glass a Liquid? benj <nobody@gmail.com> - 2015-10-03 03:05 -0400
        Re: Is Glass a Liquid? gilber34 <fafa@invalid.com> - 2015-10-02 17:07 -0500
          Re: Is Glass a Liquid? Angelo <patrizio.pan-2002@libero.it> - 2015-10-02 16:56 -0700
  Re: Is Glass a Liquid? Helmut Wabnig <hwabnig@.- --- -.dotat> - 2015-10-02 08:34 +0200
  Re: Is Glass a Liquid? "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-10-02 10:48 -0700
  Re: Is Glass a Liquid? Double-A <double-a3@hush.com> - 2015-10-02 13:25 -0700
    Re: Is Glass a Liquid? "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-10-02 15:27 -0700
  Re: Is Glass a Liquid? "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-10-02 13:30 -0700
    Re: Is Glass a Liquid? Double-A <double-a3@hush.com> - 2015-10-02 14:31 -0700
    Re: Is Glass a Liquid? benj <nobody@gmail.com> - 2015-10-03 03:19 -0400
      Re: Is Glass a Liquid? "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-10-03 10:12 -0700
        Re: Is Glass a Liquid? "hanson" <hanson@quick.net> - 2015-10-03 21:17 -0700
  Re: Is Glass a Liquid? "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-10-02 14:43 -0700

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