Why gravity rules

Eminent theoretical physicist Frank Close addresses the core physics mystery: why matter is electrically neutral, enabling gravity to rule. Atomic stability relies on the perfect balance between negative electrons and positive protons. Protons are structures of fractionally charged quarks bound by the strong color force and weak flavor force, described by the Standard Model. Exploring Grand Unified Theories, scientists seek to link leptons and quarks, predicting that this profound charge symmetry ultimately implies proton decay.