Physicists explain the properties of forces between elementary particles in terms of the Standard Model – a widely accepted framework for understanding almost everything in fundamental physics, other than gravity . (A separate theory, general relativity , is used for gravity.) In this model, the fundamental forces in nature arise from properties of our universe called gauge invariance and symmetries . The forces are transmitted by particles known as gauge bosons . [13] [14] The problem of gauge boson mass Field theories had been used with great success in understanding the electromagnetic field and the strong force , but by around 1960 all attempts to create a gauge invariant theory for the weak force (and its combination with fundamental force electromagnetism , the electroweak interaction ) had consistently failed, with ga...