In reply to:
like glass - it's just a very slow moving liquid
There is actually no conclusive evidence that suggests glass is a liquid. The following quote comes from
here.
"There have been many claims (especially by tour guides) that such glass is deformed because the glass has flowed slowly over the centuries. This has become a persistent myth, but close inspection shows that characteristic signs of flow, such as flowing around, and out of the frame, are not present. The deformations are more consistent with imperfections of the methods used to make panes of glass at the time. In some cases gaps appear between glass panes and their frames, but this is due to deformations in the lead framework rather than the glass. Other examples of rippling in windows of old homes can be accounted for because the glass was imperfectly flattened by rolling before the float glass process came into use."
I place myself in the camp that most kinds of glass (including all modern types) are not liquid.
