Time crystals could behave almost like perpetual motion machines

(PhysOrg.com) — As every young science student knows, moving objects have kinetic energy. But just how much energy does something need to move? In a new study, a pair of physicists has shown that it’s theoretically possible for a system in its lowest energy state, or ground state, to exhibit periodic motion.

More here:
Time crystals could behave almost like perpetual motion machines