Here in our Universe, there are a series of fundamental forces that all appear to operate independently of one another. There’s gravity, which is an attractive force between all objects with mass and/or energy, governed by Einstein’s general relativity and the curvature of spacetime. There’s electromagnetism, where any particle with an electric charge or an electric or magnetic field is affected by other charges and electromagnetic fields in the environment. There’s the weak nuclear force, which enables particles to change species and to decay from a heavier species into a lighter one. And there’s the strong nuclear force, which holds atomic nuclei together and binds quarks (and antiquarks) together into hadrons.

We aren’t sure whether gravity is an inherently quantum force or not, but the other three forces — electromagnetism , the weak nuclear force , and the strong nuclear force — all have quantum field theories that describe them.…