Clear As Glass

It seems that the expression clear as glass doesn't apply to the nature of glass. There is more than a little disagreement over what glass actually is.

"They’re the thickest and gooiest of liquids and the most disordered and structureless of rigid solids," said Peter Harrowell, a professor of chemistry at the University of Sydney in Australia, speaking of glasses, which can be formed from different raw materials. "They sit right at this really profound sort of puzzle."

Philip W. Anderson, a Nobel Prize -winning physicist at Princeton, wrote in 1995: "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition."

He added, "This could be the next breakthrough in the coming decade."

Thirteen years later, scientists still disagree, with some vehemence, about the nature of glass.

Peter G. Wolynes, a professor of chemistry at the University of California, San Diego, thinks he essentially solved the glass problem two decades ago based on ideas of what glass would look like if cooled infinitely slowly. "I think we have a very good constructive theory of that these days," Dr. Wolynes said. "Many people tell me this is very contentious. I disagree violently with them."

(I love that quote from Wolynes.) It is a fascinating article. One of the little blurbs that intrigued me was that glass becomes more stable over a (very) long period of time. Sort of like how concrete cures.

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5 Responses to Clear As Glass

  1. Sam L. says:

    One of my Chemistry profs told our class that glass is an extremely viscous liquid–seems old window glass in castles is thicker at the bottom than the top.  The original forms for making them were present and were measured, and were more even than the glass.

  2. Ahh the fickle nature of the state of glassLook in thy glass, and tell the face thou viewestNow is the time that face should form another;

  3. Sam says:

    I know that almost all my glasses are thickest at the bottom, except for some of the wine glasses.  Makes it harder to look through the bottom at someone else.

  4. martian says:

    I was taught the same thing, Sam L. Another indicator is that really old window glass often appears wavy or to have ripples in it. Supposedly, this is because the glass, being essentially a very viscous liquid, actually flows over very long periods of time creating the wavy ripples and resulting in added thickness at the lower end of the window pane (the direction in which it is being pulled by our old friend gravity).
     
    Someone should try the experiment of leaving a pane of window glass lieing flat on a surface that has small ridges and valleys throughout the surface in contact with the glass for about 400 years to see if the glass flows into the valleys over time. Of course this would have to be a multi-generational experiment with all of those generations being dedicated to protecting the glass at all costs so the experiment can come to fruition. Any volunteers?

  5. Martian, we just leave a note with it asking the people in the future to send it back to us with their time machine.

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