How does electroweak theory unite the electromagnetic and weak forces?

Electroweak theory unites the electromagnetic force and the weak force by treating them as different manifestations of a single, more fundamental interaction. Developed by Sheldon Lee Glashow, Abdus Salam, and Steven Weinberg, the theory constructs a gauge-invariant framework where these forces are described on an equal footing.1234

The unification relies on four gauge bosons: the massless photon for electromagnetism and three massive particles—the charged W particles and the neutral Z particle—for the weak force. While these forces appear distinct at low energies due to the large mass of the weak bosons, the theory posits that the underlying symmetry is "broken" by the Higgs field. This field endows the W and Z particles with mass, limiting the range of the weak force, while leaving the photon massless. At high energies, the strengths of these interactions become comparable, revealing their unified nature.125