50-year-mystery solved: Physicists find rare 'glueball' particle with no matter and pure force

Scientists at the Beijing Electron Positron Collider II found a rare glueball particle made purely of force. This discovery solves a 50-year mystery about subatomic states. Physicist Jin Shan said the discovery "vastly expands the boundaries of our understanding of the physical world." It confirms theories about how particles interact.