In a recent study published in Physical Review Letters, Japanese physicists created a system of more than 10,000 particles that defied Newton’s third law of motion for an hour. According to this law, passive particles exert equal forces on each other, so none can just suddenly push itself along on its own. But in devising this system, the team subjected particles to an alternating electric field that caused passive particles to spontaneously form pairs and “chase” each other in a liquid environment. For the latest study, the team suspended microscopic colloidal particles in water, then confined them between specially fabricated electrodes. Initially, the larger particles developed a larger electrical flow, attracting the smaller particles.