Robert Brout and François Englert, at the Free University of Brussels, and Peter Higgs, independently at the University of Edinburgh, propose in 1964 a theoretical mechanism that solves a central problem of particle physics: why some elementary particles have mass and others — like the photon — do not, even though the simplest mathematical equations of quantum field theory would treat all particles as equally massless. Brout, Englert, and Higgs propose that space is permeated by a field, now known as the Higgs field, with which different particles interact to different degrees: particles that interact strongly with this field acquire a large amount of mass, while those that do not interact with it, like the photon, remain massless. The mechanism also predicts the existence of a particle associated with the field itself — the Higgs boson — whose experimental detection would prove extraordinarily difficult given its expected very high mass and extremely short lifetime. The Higgs boson is finally detected in July 2012 at the Large Hadron Collider at CERN, after decades of searching, experimentally confirming, 48 years after the original theoretical prediction, the piece that completed the standard model of particle physics. Brout died in 2011, two years before the 2013 Nobel Prize in Physics, which recognized only Higgs and Englert due to the rule excluding posthumous awards; the 2004 Wolf Prize in Physics, by contrast, did include all three original authors of the mechanism.