experimentally to great precision in an extraordinarily diverse set of measurements. It has proven to be frustratingly accurate. Every experimental result so far either has agreed with the Standard Model prediction or has turned out to be wrong! Some experiments made startling new discoveries, which helped to develop the model, and others made measurements of unprecedented precision in order to test it.

One measure of the breakthroughs recognized during this 25-year period is the Nobel Prizes that have been awarded for experimental or theoretical work in this field. These are listed here:

• Burton Richter and Samuel Ting for the discovery of the charm quark;

• Martin Perl for the discovery of the tau lepton;

• Carlo Rubbia and Simon Van der Meer for the discovery of W and Z bosons;

• James Cronin and Val Fitch for the discovery of particle-antiparticle asymmetry;

• Sheldon Glashow, Abdus Salam, and Steven Weinberg for development of the unified electroweak theory;

• Jerome Friedman, Henry Kendall, and Richard Taylor for the first observation of quarks inside the proton;

• Frederick Reines for the first observation of the electron neutrino;

• Leon Lederman, Melvin Schwartz, and Jack Steinberger for the experiment establishing that the muon neutrino and the electron neutrino are separate particles; and

• Georges Charpak for the development of particle detectors.

Since 1972, high-energy physics has advanced to the stage at which almost the entire Standard Model has been established. Three lepton generations, all six quarks, and the gauge bosons for strong, electromagnetic, and weak interactions have all been observed. All of the fundamental particles have been seen, except the Higgs boson or whatever takes its place.