Is Glass a Liquid?

Stained glass is thicker at the bottom - so is it a liquid? Earth's mantle enables plate tectonics, so is it a liquid? Check out Audible: http://bit.ly/AudibleVe Sign up for the mailing list: http://www.veritasium.com Pitch drop experiment: http://www.thetenthwatch.com Thanks to Meg Rosenburg for scripting and animation, Raquel Nuno for filming and Aaron White for script consultation.