Is Glass A Solid Or An Extremely Slow Moving Liquid?

Yes old thread and old question.
Glass is not a liquid at comfortable human temperatures.
The often cited wavey glass pane windows and bluges i the panes are falicies.
Look closely at an old pane of glass that is supposedly melting. Sometimes the thickest points are the sides or top of the pane. This discounts that glass is liquid and boing pulled down by gravity. Unless of course it was mounted in one of those obsolite anti-gravity window frames.

The ones that are thickest at the bottom should show the glass melting onto and starting to wrap around or puddling up on the windows frame or stained glass lead framing. Yet it does not!

Glass panes that are a few centuries old should be paper thin at the top and all puddled up at the bottom by now, but are not.

Glass pane munufacturing was not perfected and commericalized until the late 1950s. Any glass panes you see from before then will have many optical imperfections that are noticeable when looking through them.

Bah. Science teachers were teaching this junk decades ago when I went to school (the same time they taught us the earth was cooling and their was an ice age fast on the way ... make up your minds!) and it was disproved then. In the late 80s my Materials Science prof in college chuckled over the common misconception of waviness from window glass flowing in old buildings.

Ignorant, lazy teachers continue to spout such absurdities, but with the easy access of information we have today, it's unforgivable. No excuses for lazy deadwood teachers! Pay the good ones more and fire the rest. Take that useless Masters of Education degree and go flip burgers. If you were any good, you would have gotten a real Masters in (choose one) science, history, math, etc.

Science teachers, both good and bad ones, are also at the mercy of what is known at the time they learned the facts, AND the quality of their own teachers and texts.

I had to chuckle about Floyd's high school science teacher comments. Yes, a lot of really bad information comes from teachers who are nitwits and speak from their butts. Don't get me wrong, an awesome teacher (and I've had some) really make a huge difference in kids' lives. The problem is those awesome ones (in the U.S. anyhow) don't get paid any more than the urban legend spreaders. It wouldn't be "fair" after all... Ugh. :-P

Some folks are bringing up the scale of time we are considering. Well the argument is made that glass in 200 year old buildings (like my house) has flowed under the force of gravity. That is the timescale. To be safe, take it out 1000 years or so and look at some old cathedral window glass. It would be pretty tough to find any examples of installed window glass older than that, so speaking of flow rates in geologic timeframes is extrapolating WAY beyond the limits of available samples. The assertion is that glass is visibly thicker in the bottom of old windows because of flow. That has been proven false by gifted material scientists. Any visible waviness was an artifact of production techniques. Done.

The key is what time frame are you considering? As said before, if it is geologic time, say millions of years, then glass flow is not unreasonable. However, on short time frames, human lifetime (tens of years), or even human civilization timeframe (hundreds of years), i would bet that the glass flow is negligible.
I'm not sure if the amorphous nature of pitch is the same as glass, but take a look at:
http://en.wikipedia.org/wiki/Pitch_drop_experiment