On 12/26/2012 2:14 PM, Dan Asimov wrote:
It used to be widely claimed that (apparently solid) glass was known to be liquid, because old window panes are thicker at the bottom.
As a boy, after I got my first toy of Silly Putty (in 1955. It was called "Nutty Putty"), which will slowly flow like a liquid but which can also break irregularly if struck with a hammer (like glass)* -- and learned it was a silicon compound, I was entirely convinced.
But more recently I've read that this has been found to be a myth. Rather, it is said, glass windows, etc., are in fact solids. And, the old windows were sometimes thicker at the bottom only because they were made of blown glass, with much less precision.
Yes, I think that is a myth. But insofar as glass is amorphous there are arbitrarily small energy barriers against changes of configuration and so it is technically a liquid, even though in practical terms it's a solid. Brent Meeker