Glassy state: a new field theory describes amorphous materials such as glass beads. (Courtesy: iStock/schmidt-z) Many common materials such as glass, compacted sand and toothpaste have a solid’s ...

If you don't know what we're talking about, go to your bathroom drawer now, turn your toothpaste over and look at the marking on the rigid part at the bottom of the tube. You'll likely see one of four ...