Consider a structure that moves not in space but time, crystals that change shape and move perpetually without energy, and always return to their original state. Such a structure would break the second law of thermodynamics, a cardinal rule of physics. Yet, in 2012, Nobel Laurette and theoretical physicist Frank Wilczek imagined them, what he called time crystals. Their movement isn’t of their own accord. Instead, a fracture in time’s symmetry allows for them to stay in perpetual motion.
Why crystals? Because they act atypically compared to other forms of matter. The way they construct themselves, in columns, rows, and lattices, suggests a spherical shape. But they often aren’t round or even symmetrical. Crystals therefore, are the only form of matter which compromises the spatial rule of nature. This states that all areas within space are equal and valid. Crystals break this law by repeating themselves again and again in lattices which form obscure shapes.
Space and time being related, Wilczek wondered if there were crystals who broke the temporal symmetry of nature as well. … (Big Think)