Abstract

Gravity is an extremely weak force . Consider two spheres that are close together, each with one kilogram of mass and one coulomb of electric charge, i.e., one unit each of charge and mass in Standard International Units. There will be electrical repulsion pushing them apart and gravitational attraction pulling them together, but which is bigger? It’s no contest: the electric force between these spheres is 1.35 x 1020times stronger than the gravitational force. But perhaps this difference is so large because Standard International Units depend on some rather arbitrary choices on the size of units. What about fundamental particles?