Glass Does NOT Flow

I must admit to a misconception that has stuck with me for many years and was only recently cleared up.  As a college student I was taught that glass, after it cools, flows.  In other words, the misconception states that glass windows, lenses, and anything else made of glass will change shape because glass moves over time.  I was taught this by a physics professor and remember reading it in a textbook.  Given that I was told glass flows by both a professor and a textbook, I had no reason to doubt the validity of this statement.  Since I don't work with glass everyday in my job, I had no experience to debunk this claim.

Glass can flow at high temperatures, but at room temperatures it doesn't.  Here's a great source debunking the 'glass can flow' myth.

Does Glass Flow?

What about the claim that old window panes are thicker at the bottom and thinner at the top?  Is this true?  This can be true.  Older window panes were constructed such that one side was thicker than the other.  The glass was installed such that the thicker side was on the bottom.  It has nothing to do with the glass flowing over time.

I admit that I was shocked when I learned the truth of this myth.  Even the best of us get caught by misconceptions from time to time and I certainly wouldn't classify myself as being in the "best of us" group.