Is glass a liquid? If you're familiar with Betteridge's Law of Headlines, you probably know where we're going with this already. But still, as long as I can remember, people have told me that glass is indeed a liquid, but a supremely viscous, slow-moving one at room temperature. Whenever I've looked at very old glass, mainly in old windows, whatever imperfections I've seen there have seemed like evidence to support the hypothesis that it's been flowing extremely slowly over time. I've also watched glass-blowers heat up glass and manipulate it, and it sure looks like a liquid at extremely high temperatures. So what's going on here?

Derek from Veritasium explains in the video below. The answer turns out to be surprisingly complex, and has a lot to do with how we define "liquid" and "solid." Take a few minutes to enjoy this thoughtful journey:

Note: As Derek mentioned, a relevant comparison is the pitch drip webcam, which we've covered over the years: Watch, Live, as Almost Nothing Happens and The Pitch Drip Dripped ‘Round the World.