Mechanical systems are not as simple as they appear. At Yale, quantum physicists are studying the counterintuitive behavior of seemingly simple systems using sensitive measurements. Research focuses on motion, the mechanical properties of light and electrical currents. According to quantum mechanics, all particles exhibit the properties of both waves and particles. Yale researchers have accelerated our understanding of these properties by accurately measuring persistent currents and using photons to explore the quantum properties of mirrors. This research has implications for improving laser and fiber optic equipment, as well as for upending our current understanding of the limits of time and space.