Re: Glass does not flow

[David_Anderson <dfa@FNAL.GOV>]

If glass flows it wouldn't be very good for telescope optics which are
often 1/20 of a wavelength.  How old is the 200" mirror at Palimar?  Fifty
years?  They find glass that is 5000 years old in Egypt that shows no
signs of flowing.  What about light bulbs?  They are thin, hot, and have
one atmosphere cross them?  I know.  They don't flow so it must not really
be glass.  Why not?  Because it doesn't flow.

David Anderson
dfa@fnal.gov






On Sat, 21 Aug 1999, Samuel Held wrote:

> Jim,
>         I do not URL's to back me up, but glass does not flow (at
> ambient temps).  It is a result of the glass blowing procedure way back
> when.  That is why your 130 year old windows look just the same as some
> 400-500 year old stained glass windows in churches in Europe.  These
> theory was recently (within the last 2 yrs. or so) reversed.  Any
> Material Scientists who is up on the latest research knows this.
>
>
> Sam Held
>
> -----Original Message-----
> From: Jim Green [mailto:JMGreen@SISNA.COM]
> Sent: Saturday, August 21, 1999 4:49 PM
> To: PHYS-L@lists.nau.edu
> Subject: Re: Glass does not flow
>
>
> Here is someone who is learning physics from "Earth&Sky! Wow!
>
> Anyone who thinks that glass doesn't flow is welcome to visit my 130 yr
> old
> house and look out the windows.
>
> In materials science common glass is clearly thought to be a fluid.  It
> has
> no long range crystalline structure and clearly flows.
>
> Jim Green
>
> At 01:52 PM 8/21/99 -0500, you wrote:
> > For those of you that think that glass flows under its own weight you
> > might find this URL a good place to start.
> > (www.earthsky.com/1997/esmi971014.html) Then go to the links.
> > Do not feel too bad about holding this common belief.  One can even
> find
> > it in Feynman's Lecture Series
> >
> > David Anderson
> > DFA@fnal.gov
>
> Jim Green
> mailto:JMGreen@sisna.com
> http://users.sisna.com/jmgreen