n the 1940s, Feynman and others developed QED, which describes electromagnetic particle interactions. In the 1960s, Gell-Mann and others developed QCD, which describes the strong nuclear force, the forThe Standard Model of particle interactions is one of the most successful theories of all time. Devised between 1970 and 1973, this model incorporates everything that is known about particle interactions, including special relativity, quantum electrodynamics (QED), electroweak theory, quantum chromodynamics (QCD). The only thing left out of the theory is gravity.

The Standard Model is the culmination of 20th century theoretical particle physics. In the 1920s, Heisenberg and Schrodinger independently derived quantum mechanics, which accurately describes microscopic (atomic and smaller) systems. In 1928, Dirac supplanted quantum mechanics with a version which incorporates special relativity. His new version predicted the existence of antimatter, which was experimentally verified in 1932. In the 1940s, Feynman and others developed QED, which describes electromagnetic particle interactions. In the 1960s, Gell-Mann and others developed QCD, which describes the strong nuclear force, the for

ns, including special relativity, quantum electrodynamics (QED), electroweak theory, quantum chromodynamics (QCD). The only thing left out of the theory is gravity.

The Standard Model is the culmination of 20th century theoretical particle physics. In the 1920s, Heisenberg and Schrodinger independently derived quantum mechanics, which accurately describes microscopic (atomic and smaller) systems. In 1928, Dirac supplanted quantum mechanics with a version which incorporates special relativity. His new version predicted the existence of antimatter, which was experimentally verified in 1932. In the 1940s, Feynman and others developed QED, which describes electromagnetic particle interactions. In the 1960s, Gell-Mann and others developed QCD, which describes the strong nuclear force, the for

ination of 20th century theoretical particle physics. In the 1920s, Heisenberg and Schrodinger independently derived quantum mechanics, which accurately describes microscopic (atomic and smaller) systems. In 1928, Dirac supplanted quantum mechanics with a version which incorporates special relativity. His new version predicted the existence of antimatter, which was experimentally verified in 1932. In the 1940s, Feynman and others developed QED, which describes electromagnetic particle interactions. In the 1960s, Gell-Mann and others developed QCD, which describes the strong nuclear force, the forms. In 1928, Dirac supplanted quantum mechanics with a version which incorporates special relativity. His new version predicted the existence of antimatter, which was experimentally verified in 1932. In the 1940s, Feynman and others developed QED, which describes electromagnetic particle interactions. In the 1960s, Gell-Mann and others developed QCD, which describes the strong nuclear force, the forn the 1940s, Feynman and others developed QED, which describes electromagnetic particle interactions. In the 1960s, Gell-Mann and others developed QCD, which describes the strong nuclear force, the force which binds quarks together. In 1967, Glashow, Weinberg, and Salam developed the electroweak theory, a theory which unifies the electromagnetic and weak nuclear forces. Between 1970 and 1973, several physicists tied all these theories together into the Standard Model.

Despite its enormous success, most physicists are not entirely happy with the Standard Model. It is not at all an elegant theory, having 19 free parameters which need to be put in by hand. Many would rather see a theory with no free parameters which also incorporates gravity. String theory seems to be the most promising avenue for such a theory, which would be a Unified Field Theory, or a Theory of Everything. Unfortunately, despite having been studied intensively for over 20 years, not a single experimentally verifiable