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Is Glass a Liquid?

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  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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#524175 — Is Glass a Liquid?

Is Glass a Liquid?
> https://www.youtube.com/watch?v=c6wuh0NRG1s

> Stained glass is thicker at the bottom - so is it a liquid? Earth's
> mantle enables plate tectonics, so is it a liquid?




-- 

sci.physics is an unmoderated newsgroup dedicated
to the discussion of physics, news from the physics
community, and physics-related social issues.

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#524181 — no, and yes

no, and yes; it's similar, because
glass does not actually flow in any measurable sense at r.t
(it is rather just results from coolng at the factory

so, anyway, I used to berate the ideal
of a flowing mantle, since seismicity is primarily the result
of waves in a solid.  then,
about pi y.a, I went to a symposium
by a guy that works for oilcos (yay, and
he gave a perfectly recondite mechanism [although
I have ne'er since seen or heard a thing

> > Stained glass is thicker at the bottom - so is it a liquid? Earth's
> > mantle enables plate tectonics, so is it a liquid?
> 
> 
> 
> 
> -- 
> 
> sci.physics is an unmoderated newsgroup dedicated
> to the discussion of physics, news from the physics
> community, and physics-related social issues.

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#524182

Sam Wormley <swormley1@gmail.com> wrote:
> Is Glass a Liquid?

Holy fucking shit, not again, spamming shit head.


-- 
Jim Pennino

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#524198

On 10/01/2015 08:11 PM, Sam Wormley wrote:
> Is Glass a Liquid?
>> https://www.youtube.com/watch?v=c6wuh0NRG1s
>
>> Stained glass is thicker at the bottom - so is it a liquid? Earth's
>> mantle enables plate tectonics, so is it a liquid?

Oh look Muffy! Sammy is cut and pasting his favorite physics moron. As 
usual he's totally wrong again! Clearly more into journalism lies than 
science (just like you Sam).

No stained glass does not sag in old church windows. That is a given. 
However his statement that glass is a solid and does not flow is 
nonsense. It's been known forever that most glass is just a very viscous 
liquid. It's easy to prove. But it's so much easier to just remain stupid.

Today what some people like to call glass (like say the white opal glass 
invented in the 1930s for light shades) and even more so, the white 
"corningware" dishes are indeed solids because they contain a crystal 
structure which gives them their properties. People still term them 
"glass" however which just adds to the confusion.

Of course your idiot "boy" is already confused and is using his media 
skills to confuse any who will listen to him. Sad. Almost as sad as you 
for thinking he's right.

Especially since we went through this with you not too long ago.

Here, Sammy. Go read this:

http://www.alz.org/alzheimers_disease_10_signs_of_alzheimers.asp




-- 
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       /::\  \       /::\  \       /::|  |         \:\  \
      /:/\:\  \     /:/\:\  \     /:|:|  |     ___ /::\__\
     /::\~\:\__\   /::\~\:\  \   /:/|:|  |__  /\  /:/\/__/
    /:/\:\ \:|__| /:/\:\ \:\__\ /:/ |:| /\__\ \:\/:/  /
    \:\~\:\/:/  / \:\~\:\ \/__/ \/__|:|/:/  /  \::/  /
     \:\ \::/  /   \:\ \:\__\       |:/:/  /    \/__/
      \:\/:/  /     \:\ \/__/       |::/  /
       \_:/__/       \:\__\         /:/  /
                      \/__/         \/__/

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#524207

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...

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#524212

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

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#524231

A house beam sags with Gravity also-
is it liquid?

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#524235

Il giorno venerdì 2 ottobre 2015 15:33:59 UTC+2, john ha scritto:
> A house beam sags with Gravity also-
> is it liquid?

I think that the distinction is bound to reversibility (of shape) when 
the stress is removed.
A crystal is elastic, a liquid is also viscous, and its shape can be 
permanently modified (without rupture).

regards
Angelo

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#524246

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.

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.

Glass is a very viscous liquid. Period.

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 
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.

Note that the more heat you apply the more bonds are broken and moved 
and hence the more the material can move and the less viscous it 
becomes. Gosh the theory actually works!

You're welcome.

-- 
         ___           ___           ___            ___
        /\  \         /\  \         /\__\          /\  \
       /::\  \       /::\  \       /::|  |         \:\  \
      /:/\:\  \     /:/\:\  \     /:|:|  |     ___ /::\__\
     /::\~\:\__\   /::\~\:\  \   /:/|:|  |__  /\  /:/\/__/
    /:/\:\ \:|__| /:/\:\ \:\__\ /:/ |:| /\__\ \:\/:/  /
    \:\~\:\/:/  / \:\~\:\ \/__/ \/__|:|/:/  /  \::/  /
     \:\ \::/  /   \:\ \:\__\       |:/:/  /    \/__/
      \:\/:/  /     \:\ \/__/       |::/  /
       \_:/__/       \:\__\         /:/  /
                      \/__/         \/__/

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#524315

On Friday, October 2, 2015 at 12:19:53 PM UTC-4, benj wrote:
> 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...

Sources say everything between The Alpha and The Omega. Including the
bounding endpoints. All one has to do is cherry pick sources to
satisfy one's own biases, universal biases, of course ...whoKnew.

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

Yes. It's also a function of temperature, molten glass is still
glass. If it were not fluid, then Venetion Glass Blowers would have
built nothing. Not to mention, molten steel is also a fluid. Phase
(Solid, Fluid, Plasma, ...) Space diagrams are like a topic in
undergraduate level courses. Not to mention, common sense. At least,
should be, for any physicist Physicist PHYSICIST. Save Sam.

The real baiting issue with SamBot is: Is glass a universal singular
word with one and only one meaning and interpretation? Obiously
not. The old: If one can't teach them any real science, then might as
well confound them English terminology. Bad pronunciation, FAIL!

In Hindi glass is sheesha. Guess if it's a liquid in that Language.

> 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!

The evidentiary pictures they've shown of church windows do look neat
and impressive, but that effect was more likely due to persistent
solar radiation slowly heating the glass over five centuries.

> 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.

Under the right circumstances, I could make it 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 
> 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.

I was going to say exactly that. I was... why does nobody believe me?!
 
> Note that the more heat you apply the more bonds are broken and moved 
> and hence the more the material can move and the less viscous it 
> becomes. Gosh the theory actually works!
> 
> You're welcome.
> 
> -- 
>          ___           ___           ___            ___
>         /\  \         /\  \         /\__\          /\  \
>        /::\  \       /::\  \       /::|  |         \:\  \
>       /:/\:\  \     /:/\:\  \     /:|:|  |     ___ /::\__\
>      /::\~\:\__\   /::\~\:\  \   /:/|:|  |__  /\  /:/\/__/
>     /:/\:\ \:|__| /:/\:\ \:\__\ /:/ |:| /\__\ \:\/:/  /
>     \:\~\:\/:/  / \:\~\:\ \/__/ \/__|:|/:/  /  \::/  /
>      \:\ \::/  /   \:\ \:\__\       |:/:/  /    \/__/
>       \:\/:/  /     \:\ \/__/       |::/  /
>        \_:/__/       \:\__\         /:/  /
>                       \/__/         \/__/

-- Mahipal

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#524342

Mahipal, 14 August 2015:

A lot of posters do not like me. Apparently. By a lot, I mean a lot
Lot LOT of people. I hurt their sensibilities. It's like I was once
married to them all. Regardless... I am leaving Usenet now and
forever. It's their playground and I obviously am not welcome.

So goodbye Goodbye GOODBYE.

https://groups.google.com/forum/#!original/sci.physics/UIfOYtrXEMc/DCrgBtWzmxUJ

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#524345

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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#524352

On 10/02/2015 10:41 PM, Angelo wrote:
> 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.

As you and I point out, things are not quite as neat as I presented them 
as things people call glass are a mixture of things including crystals. 
Some things people call glass are actually crystalline and don't sag. So 
there is a lot devil in the details. But generally speaking glasses of 
the ordinary window type are viscous.






-- 
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       /::\  \       /::\  \       /::|  |         \:\  \
      /:/\:\  \     /:/\:\  \     /:|:|  |     ___ /::\__\
     /::\~\:\__\   /::\~\:\  \   /:/|:|  |__  /\  /:/\/__/
    /:/\:\ \:|__| /:/\:\ \:\__\ /:/ |:| /\__\ \:\/:/  /
    \:\~\:\/:/  / \:\~\:\ \/__/ \/__|:|/:/  /  \::/  /
     \:\ \::/  /   \:\ \:\__\       |:/:/  /    \/__/
      \:\/:/  /     \:\ \/__/       |::/  /
       \_:/__/       \:\__\         /:/  /
                      \/__/         \/__/

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#524307

On 10/2/2015 1:55 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:
>>

> 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).
>

but that is not flow.  that is just sag,

the mounts sag too, and they are steel.

large refractors cost to much to build the lens, and have a chance it
will fracture.

Refractors you can spin in an oven and get the surface close, cheaper

you still have sag problems with the large refractors



> regards Angelo
>

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#524328

Il giorno sabato 3 ottobre 2015 00:08:06 UTC+2, gilber34 ha scritto:
> On 10/2/2015 1:55 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:
> >>
> 
> > 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).
> >
> 
> but that is not flow.  that is just sag,

You are right. I had mixed up the two terms, sorry. Now I think 
'flow of glass' can be equated to an inelastic deformation, 'sag' 
to an elastic one.
 
> the mounts sag too, and they are steel.

Yes, deformation of (real) crystals is elastic, the strain grows with 
the stress, and then at a certain point they break.

My point was that glass can of course bend under stress but in this case 
both mechanisms are at work. 
Strain due to deformation is quasi-reversible in the sense that if the 
stress is quickly removed the original shape is recovered, but if the 
stress is mantained for a long time that allows a different relieving: 
viscous (or plastic) sliding at miscroscopic level occurs (slowly) and 
the piece of glass has now acquired a new shape.

Thus a large, thin lens held by its edges loses in time (though inperceptibly at naked eye) its perfect shape, so becoming useless.

OK for the rest.
 
> large refractors cost to much to build the lens, and have a chance it
> will fracture.
> 
> Refractors you can spin in an oven and get the surface close, cheaper
> 
> you still have sag problems with the large refractors

regards
Angelo

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#524210

On Thu, 1 Oct 2015 19:11:43 -0500, Sam Wormley <swormley1@gmail.com>
wrote:

>Is Glass a Liquid?
>> https://www.youtube.com/watch?v=c6wuh0NRG1s
>
>> Stained glass is thicker at the bottom - so is it a liquid?

Show me one (1) such glass.

The manufacturing process at the time was not good enough to give
uniform thickness. And thaTs all.

The "bottom" story is unverified nonsense.

w.

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#524253

On Thursday, October 1, 2015 at 5:11:53 PM UTC-7, Sam Wormley wrote:
> Is Glass a Liquid?
> > https://www.youtube.com/watch?v=c6wuh0NRG1s
> 
> > Stained glass is thicker at the bottom - so is it a liquid? Earth's
> > mantle enables plate tectonics, so is it a liquid?
> 
> 
> 
> 
> -- 
> 
> sci.physics is an unmoderated newsgroup dedicated
> to the discussion of physics, news from the physics
> community, and physics-related social issues.

Glass is a solid.I know why its a little wider where its side is siting.TreBerty 

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#524281

On Thursday, October 1, 2015 at 5:11:53 PM UTC-7, Sam Wormley wrote:
> Is Glass a Liquid?
> > https://www.youtube.com/watch?v=c6wuh0NRG1s
> 
> > Stained glass is thicker at the bottom - so is it a liquid? Earth's
> > mantle enables plate tectonics, so is it a liquid?


No, it is plastic.  Latin plasticus.

Double-A

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#524311

On Friday, October 2, 2015 at 1:25:27 PM UTC-7, Double-A wrote:
> On Thursday, October 1, 2015 at 5:11:53 PM UTC-7, Sam Wormley wrote:
> > Is Glass a Liquid?
> > > https://www.youtube.com/watch?v=c6wuh0NRG1s
> > 
> > > Stained glass is thicker at the bottom - so is it a liquid? Earth's
> > > mantle enables plate tectonics, so is it a liquid?
> 
> 
> No, it is plastic.  Latin plasticus.
> 
> Double-A

AA Its wieght when cooling made it thicker when standing on the side facing the floor.Only low wit thinkers say its a liquid and not a solid at room temp. Bad science by  imperial thinkers and repeated by parrots.Like poles flip.and comets are snow balls. TreBert

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#524284

On Thursday, October 1, 2015 at 5:11:53 PM UTC-7, Sam Wormley wrote:
> Is Glass a Liquid?
> > https://www.youtube.com/watch?v=c6wuh0NRG1s
> 
> > Stained glass is thicker at the bottom - so is it a liquid? Earth's
> > mantle enables plate tectonics, so is it a liquid?
> 
> 
> 
> 
> -- 
> 
> sci.physics is an unmoderated newsgroup dedicated
> to the discussion of physics, news from the physics
> community, and physics-related social issues.

Glass as a solid does not FLOW.As heated to liquid and when made it flows.That is a clew why old time glass is fatter on one side.Not hard to figure.TreBert

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