New submitter omaha393 writes: Researchers have addressed a perplexing issue in physics: the existence of time crystals. Time crystals, previously only hypothetical in nature, are structures that oscillate without any external energy supplied. The idea of time crystals set off a massive feud among physicists, arguing that such a state of matter could not exist. As leading time crystal proponent Frank Wilczek describes it: "conceptually, it is a clock that ticks forever without being wound." With the paper published in Nature Wednesday, researchers showed their method of production and the unusual nature of time crystals, which owe their oscillation properties to never achieving a state of equilibrium. From a report on Phys.org: Ordinary crystals such as diamonds, quartz or ice are made up of molecules that spontaneously arrange into orderly three-dimensional patterns. The sodium and chlorine atoms in a crystal of salt, for example, are spaced at regular intervals, forming a hexagonal lattice. In time crystals, however, atoms are arranged in patterns not only in space, but also in time. In addition to containing a pattern that repeats in space, time crystals contain a pattern that repeats over time. One way this could happen is that the atoms in the crystal move at a certain rate. Were a time crystal of ice to exist, all of the water molecules would vibrate at an identical frequency. What is more, the molecules would do this without any input from the outside world. [...] Shivaji Sondhi, a Princeton professor of physics said that the work addresses some of the most fundamental questions about the nature of matter. "It was thought that if a system doesn't settle down and come to equilibrium, you couldn't really say that it is in a phase. It is a big deal when you can give a definition of a phase of matter when the matter is not in equilibrium," he said.