1940s Richard Feynman and other physicists develop quantum electrodynamics (QED), which describes quantum-level interactions due to the electromagnetic force.
1960s The standard model of particle physics reveals the full range of subatomic particles known so far and the interactions that affect them.
1970s String theory falls out of favor temporarily as quantum chromodynamics appears to offer a better explanation of the strong nuclear force.
1980s Lee Smolin and Italian Carlo Rovelli develop the theory of loop quantum gravity, which removes the need to theorize hidden extra dimensions.
Put simply, string theory is ...