Nobel Prize "for his contributions to the theory of the unified weak and electromagnetic interaction between elementary particles, including, inter alia, the prediction of the weak neutral current".
Only four kinds of fundamental interactions rule the Universe: gravity, electromagnetism, the weak force (responsible of radioactivity and thermonuclear processes that take place in the interior of the stars), and the strong force (that keeps protons and neutrons tightly together in the atomic nucleus). If the Universe is a single entity, it is natural to conclude that the fundamental interactions that govern it should also be the expression of a mechanism that can be unified.
After the first unification in physics performed in the XIX century by James Clerk Maxwell, who showed that electricity and magnetism are two faces of a single phenomenon, Glashow was the one making a further step in the direction of unifying the remaining interactions. In 1960 he constructed a theoretical model that showed that Maxwell's electromagnetism and the weak force, characterized by Enrico Fermi, were nothing but two manifestations of a single unified interaction afterwards named electroweak. This is particularly remarkable taking into account that both forces are manifestly quite different in intensity and other features. Glashow's theory predicted the existence of a new particle, the Z boson, whose discovery at CERN's premises, in 1973, constituted one of the milestones in the history of modern physics.
