When I took Calculus-based Physics in college (2003), my professor taught us that glass was an "extremely viscous fluid." When was glass reclassified as an amorphous solid?
Smperron (talk) Your professor was simply incorrect. Glass never was, and has never been, an "extremely viscous fluid". Molten glass is a "molecular liquid" where the viscosity depends on temperature. 220.127.116.11 22:14, 13 December 2012 (UTC)
"Extremely viscous fluid" is just another way to describe an amorphous solid (as opposed to the crystallic solid). There is no sharp cut-off between these states. Just at some point it starts feeling solid enough, so it gets called a solid. See the Pitch Drop Experiment  for an example (though glass is obviously harder than pitch). 18.104.22.168 19:21, 16 January 2014 (UTC)
I had a chemistry professor in 2011 tell me that glass flowed, even citing old buildings with thicker glass on the bottom. I tried to argue against it, but I was interrupting a lecture. I discussed it with some students later, though. 22.214.171.124 00:49, 1 February 2014 (UTC)