As they say in the article,
“The name sounds like a prop from Doctor Who, but it has roots in actual physics. Time crystals are hypothetical structures that pulse without requiring any energy” – Scientific American
The name makes it sound as if time crystallizes into something solid, but what happens is less obvious, weirder, and more physical, almost. A time crystal is a group of atoms that interact in a very specific way. Normally, a group of atoms will reach some steady state where they settle down and can’t change without additional energy. But, within quantum mechanics, nothing is every truly still. By taking advantage of that change, researchers have created groups of atoms that never settle down but continue to dance at a very precise speed, like the tone from a ringing crystal. At the quantum level, the matter may never coalesce into something we’d consider solid, so it isn’t matter either, just an event in time. The significance is that the frontiers of physics just expanded into a realm that was thought impossible until the last few years. Matterless materials will undoubtedly have surprising properties. For now, time crystals are being investigated for pure science, quantum computers, and sensitive sensors.