In 1979, some six years after the experimental discovery of the neutral currents—i.e. the discovery of the inferred existence of the Z boson —but after the 1978 experimental discovery of the theory's predicted amount of parity violation due to Z bosons' mixing with electromagnetic interactions, Weinberg was awarded the Nobel Prize in physics with Glashow and Salam, who had independently proposed a theory of electroweak unification based on spontaneous symmetry breaking.