Paul Dirac
Paul Dirac | |
|---|---|
| Born | Paul Adrien Maurice Dirac 8 August 1902 Bristol, England |
| Died | 20 October 1984 Tallahassee, Florida, United States |
| Nationality | British |
| Alma mater | University of Bristol; University of Cambridge |
| Known for | Dirac equation; prediction of antimatter; Fermi–Dirac statistics; magnetic monopole; large numbers hypothesis |
| Awards | Nobel Prize in Physics (1933, shared with Erwin Schrödinger) |
| Scientific career | |
| Fields | Theoretical physics, quantum mechanics, quantum field theory |
| Institutions | University of Cambridge; Florida State University |
Paul Adrien Maurice Dirac (1902–1984) was the theoretician who put quantum mechanics into relativistic form, and in doing so predicted antimatter from an equation rather than from an experiment. He is invoked on this wiki more often than almost any other twentieth-century physicist, for two reasons that have little to do with each other: the discarded negative-energy solutions of his equation, and his late, explicit defence of an aether.
Contributions
Dirac's 1928 relativistic wave equation for the electron accounted for electron spin as a structural consequence rather than an added postulate, and reproduced the fine structure of hydrogen. Its solutions came in two families, one of negative energy; Dirac's resolution was the "sea" — a filled continuum of negative-energy states whose vacancies would behave as positively charged particles. The positron was found in cosmic rays by Carl Anderson in 1932.
He shared the 1933 Nobel Prize in Physics with Erwin Schrödinger. His other lasting contributions include Fermi–Dirac statistics, the transformation theory that unified matrix and wave mechanics, the delta function, the first quantum theory of radiation emission and absorption, the 1931 argument that a single magnetic monopole anywhere would explain electric charge quantisation, and the large numbers hypothesis of 1937 — the observation that certain dimensionless ratios in physics are all of order 1040, from which he inferred that the gravitational constant might vary with the age of the universe. His textbook The Principles of Quantum Mechanics (1930) shaped how the subject has been taught ever since.
In the early 1950s Dirac published arguments — including a 1951 note in Nature titled "Is there an Aether?" — that the quantum vacuum could be given a velocity distribution and that the relativistic objection to a material aether was not decisive.
On this wiki
Don L Hotson makes the strongest claim: in Dirac's Equation and the Sea of Negative Energy, Part 1 and Dirac's Equation and the Sea of Negative Energy, Part 2 he argues that abandoning the negative-energy sea in favour of renormalised quantum field theory was the central wrong turn of twentieth-century physics, and builds a cosmology of electron–positron pairs on the retained sea. Don L Hotson's model is developed further here in Dynamics of Black Holes and Structure Formation in the Hotson - Westergard Universe Model and Degenerate Angular Momentum in the Hotson-Westergard Universe Model.
Peter Rowlands takes the equation as foundational rather than defective. In Breaking the Dirac Code and Zero to Infinity he develops a nilpotent form of the Dirac algebra from which he claims the structure of particle physics can be derived. Waldyr Alves Rodrigues pursues the same formal territory in The Many Faces of Maxwell, Dirac and Einstein Equations: A Clifford Bundle Approach, and Martin Müller proposes replacements in Genuine Subharmonic Equations to Replace Those of Schrödinger and Dirac.
Dirac's aether is a live thread. Jean Pierre Vigier, a leading advocate of the stochastic interpretation of quantum mechanics, worked explicitly within a Dirac-style real vacuum; see Jean-Pierre Vigier and the Stochastic Interpretation of Quantum Mechanics and Interactions of Internal Inertial and Phase Space Motions in Dirac's Real Aether Model. Ian McCausland documents Dirac's own assessment of the relative merits of Einstein and Lorentz in Dirac on Einstein and Lorentz (1996) — a citation of some weight in the relativity debates catalogued here, since Dirac cannot be dismissed as an outsider.
The large numbers hypothesis has its own following. Wladimir Guglinski applies it to planetary growth in The Expanding Earth: Some Consequences of Dirac's Gravitation Hypothesis (see Expanding Earth), and Manfred Geilhaupt revisits the coincidences in Electron, Universe, and the Large Numbers Between.