Some laws of physics are so fundamental that they’ve served as the baseline for science for centuries. But with technological advancements, physicists can—albeit temporarily—create small worlds that evade these laws. And when they do, strange things occur. 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. “This research demonstrates that the breaking of action-reaction symmetry is a fundamental principle that generates new collective motions and self-organization of matter,” Yutaka Sumino, the study’s co-author and a physicist at the Tokyo University of Science in Japan, said in a statement.
A physical standstill To quote Isaac Newton himself, the third law of motion mandates that “mutual actions of two bodies upon each other are always equal and directed to contrary parts.” The key here is symmetry—a reciprocal relationship between action and reaction.
