The English physicist Paul Adrien Maurice Dirac, b. Aug. 8, 1902, d. Oct. 22, 1984, made significant contributions to the development of quantum mechanics. In September 1925 he read an account of a lecture on quantum mechanics by the German physicist Werner Heisenberg, and quickly devised a number of new mathematical formulations of quantum mechanics that have since proved to be of great importance. In his first publication, in November 1925, Dirac elaborated a method for deriving the equation of motion from quantum mechanics, and a few months later he clearly defined a number of concepts that were to play a major role in the field.

Dirac's fame stems from his formulation in 1928 of a mathematical description of elementary particles that accords with both quantum mechanics and the theory of relativity. The Dirac equation was surprising in that it involved matrices (arrays of numbers that may assume different forms for different observers) rather than scalar quantities. These properties of the Dirac equation were of major importance for theoretical physics. Moreover, to everyone's astonishment, the Dirac equation provided the first rigorous description of the spin of elementary particles. Even more surprisingly, the equation had solutions for negative particle mass, from which Dirac concluded that each particle should have an anti-particle. This and other consequences of the equation were subsequently confirmed by experiment; Dirac is therefore considered to be one of the founders of modern quantum electrodynamics.

Dirac was Lucasian Professor of Mathematics at Cambridge from 1932 to 1969 and professor of physics at Florida State University, from 1971 until his death. In 1933 he was awarded the Nobel Prize for physics with Erwin Schrodinger.