(1902-1984) British physicist who worked out a version of quantum mechanics consistent with special relativity. The existence of antiparticles, such as the positron (positive electron), was one of its predictions. He shared the Nobel Prize for Physics 1933 with Austrian physicist Erwin Schrödinger.
Dirac was born and educated in Bristol and from 1923 at Cambridge, where he was professor of mathematics 1932–69. From 1971 he was professor of physics at Florida State University.
In 1928 Dirac formulated the relativistic theory of the electron. The model was able to describe many quantitative aspects of the electron, including such properties as the half-quantum spin and magnetic moment, and introduced the first antiparticle.
Dirac noticed that those particles with half-integral spins obeyed statistical rules different from the other particles. For these particles, Dirac worked out the statistics, now called Fermi–Dirac statistics because Italian physicist Enrico Fermi had done very similar work. These are used, for example, to determine the distribution of electrons at different energy levels.
Dirac also worked on the large-number hypothesis. This deals with pure, dimensionless numbers, such as the ratio of the electrical and gravitational forces between an electron and a proton, which is 1039.