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
--I deny this. I claim, it is at least in principle possible for an amorphous solid to exist in which any change requires at least a fixed energy change. One simple example would be usual periodic packing of bricks, but each brick is in one of 2 orientations ("upside down" or "rightside up") selected randomly, and any switch takes 1 electron volt to get you over the barrier. Also, re the claim glass is a "liquid with very high viscosity" how about solid crystalline metals? They can be deformed. In fact, they are a lot more deformable than glass. So are they liquids with high viscosity?