New Muonium Beam Enables First Gravity Test on Second‑Generation Particles

Scientists have produced a controlled beam of muonium, an exotic atom composed of a positive muon and an electron. The achievement opens the door to the first experiment that will measure how gravity acts on second‑generation particles. According to Einstein’s general relativity, all masses should fall at the same rate regardless of composition. By dropping the muonium beam in a precisely calibrated gravitational field, researchers will test whether the muon's heavier cousin of the electron experiences the same acceleration as ordinary matter. Any deviation would challenge the universality of free fall and could signal the existence of a previously unknown force. The experiment is slated to begin later this year at a dedicated muon facility, marking a milestone in precision tests of fundamental physics.