I thought both Cecil and Snopes squashed this legend, but a quick search here and there found nothing. I think the old window makers put the thick side down because it was more stable than sideways or thick side up.
Glass was made by spinning it while molten. When it cooled the outside edge was thicker than the center. Because it was labor intensive, the thicker parts were used along with the thinner, more uniform parts.
Well I put my money on Cecil. How would one go about calculating the rate of flow of glass anyway?
Just so everyone knows this thread was not put up to question Cecil et al, but as a mockery of Newsweek’s amazing level of ignorance. The question of “glass flowing” within the observable age of the universe is not going to happen. It’s just stunning that someone writing about science for a major media publication would not know this old canard is false.
We did this one two days ago.
http://boards.straightdope.com/sdmb/showthread.php?t=472928&highlight=glass
Sadly it’s not stunning at all. Most people, including most journalists, know very little about science, except dimly remembered factoids like this.