The Higgs was born of wishful thinking. It was introduced in the 1960s by British theoretical physicist Peter Higgs of the University of Edinburgh to help plug a huge gap in the understanding of quantum physics. The simplest and most elegant models require that all elementary particles should have the same mass: zero. But every moment of human experience asserts otherwise, and experiments show that the masses of elementary particles in fact differ by many orders of magnitude. Physicist Steven Weinberg of the University of Texas at Austin and Pakistani theorist Abdus Salam used the Higgs concept to bring theory in line with reality.
In Weinberg’s synthesis the Higgs field is like a sea of molasses that fills all of space. It resists the movement of particles to varying degrees. The more a particle interacts with the Higgs field, the greater the resistance and the heavier the particle. The symmetry of the standard model is thus restored because mass is no longer seen as an intrinsic property of matter. All elementary particles weigh nothing until they interact with the Higgs field. Variations in Higgs field interactions are the only explanation physicists have for the fact that the heftiest known particle weighs 200,000 times as much as the lightest one, while photons weigh nothing at all.
“The Higgs field, the standard model, and our picture of how God made the universe depend on finding the Higgs boson,” wrote Nobel laureate Leon Lederman in his 1993 book The God Particle. His book championed the Superconducting Supercollider, the $10 billion accelerator he had designed to nab the Higgs. Because it is thought to be the most massive of all elementary particles, the Higgs boson would show up only in ultrahigh-energy collisions. The Supercollider’s particle beams would have collided at 20 times the energy of the Tevatron’s. But soon after The God Particle was published, Congress pulled the plug on the project.
That was the first of several heartbreaks for Higgs seekers. The next came at the Large Electron Positron, or LEP, collider, a 17-mile-long particle smasher on the Franco-Swiss border at the European Center for Nuclear Research, called CERN for short. In August 2000, after a decade of collisions at gradually escalating energies, the collider team saw data that hinted at the presence of the Higgs. “We were sure we were going to find the Higgs particle,” says experimental physicist Christopher Tully of Princeton University, who heads the CERN search. “It was a very dramatic moment.”
Unfortunately, the LEP collider was shut down for good in November 2000 to make way for the $2.5 billion Large Hadron Collider, scheduled to come online in 2007. The LHC will be supported by 5,000 physicists and 500 research institutes around the world. It will hurl particles with seven times the energy of the Tevatron. “The LHC discovery of the Higgs is guaranteed—if it exists,” says experimental physicist Suyong Choi of Fermilab.