Paul Dirac

(8 August 1902 – 20 October 1984)

Paul Dirac

Paul Dirac

Paul Adrien Maurice Dirac was probably the greatest English physicist since Sir Isaac Newton. He was born in Bristol to a Swiss immigrant father and Cornish mother.

Physicist

At the University of Bristol he obtained a degree in electrical engineering in 1921 and a BA in applied mathematics in 1923. A grant then enabled him to enter St John’s College, Cambridge, where he studied the new ideas of relativity and quantum theory and gained a PhD in 1926. He was Lucasian Professor of Mathematics at Cambridge from 1932 to 1969. His later years were spent in Florida.

Dirac’s Principles of Quantum Mechanics (1930) is still a standard textbook on the subject. He showed that the Heisenberg matrix mechanics and the Schrödinger wave mechanics formulations of quantum theory were mathematically equivalent.

His main achievement was the formulation of the Dirac equation for the electron, combining relativity with the quantum wavefunction. This explained quantum ‘spin’ as a relativistic effect. Symmetry in the equation indicated a second solution, thus predicting the possible existence of ‘antimatter’. The anti-particle of the electron, named the ‘positron’ was observed experimentally by Carl Anderson in 1932. Dirac shared the Nobel Prize in physics for 1933 with Erwin Schrödinger.

“God is a product of the human imagination”

On religion Dirac stated:

If we are honest — and scientists have to be — we must admit that religion is a jumble of false assertions, with no basis in reality. The very idea of God is a product of the human imagination. It is quite understandable why primitive people, who were so much more exposed to the overpowering forces of nature than we are today, should have personified these forces in fear and trembling. But nowadays, when we understand so many natural processes, we have no need for such solutions. [1927, quoted by Heisenberg 1972]

His fundamental belief, according to John Polkinghorne, was that the laws of nature should be expressed in beautiful equations.

A plaque bearing the Dirac equation was unveiled at Westminster Abbey, London by Stephen Hawking in 1995. Bristol has a Dirac Road, and there is a blue plaque on his childhood home 15 Monk Road.

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