Why is he famous?

He discovered the Dirac equation and was one of the founding fathers of quantum mechanics and quantum field theory.

In the 1920s and 1930s, together with Bohr, Heisenberg, Schrödinger and Pauli, he opened up the field of quantum physics, changing the course of science. In 1933, aged 31, he became the youngest theoretician to win a Nobel prize.From John Carey's review for The Sunday Times (January 11, 2009) of the book "The Strangest Man: the Hidden Life of Paul Dirac" by Graham Farmelo

Biography

• P. A. M. Dirac: Some strangeness in the proportion by Jeremy Bernstein
• "The Strangest Man" by Graham Farmelo

Anecdotes

I used to be pen-pal with a lady who did experimental nuclear physics at Harwell starting in the 1950s. In her autobiography she told of seeing Dirac at a Cavendish lecture. One from the audience asked, "Professor Dirac, I do not understand your fourth equation down on the left-hand side of the blackboard." Dirac said nothing, but just stared placidly into space. The lecture Chairman asked, "Professor Dirac, are you prepared to answer that question?" Dirac's response was "Oh. Was that a question? I thought it was just a statement of fact."http://physicsandphysicists.blogspot.de/2009/10/pam-diract-some-strangeness-in.html

"Dick Feynman told the story that when he first met Dirac at a conference, Dirac said after a long silence, "I have an equation; do you have one too?""Quantum Field Theory in a Nutshell" by A. Zee

Dirac said “I was taught at school never to start a sentence without knowing the end of it.” This explains a lot. Dirac’s famously taciturn and precise nature spawned many “Dirac stories”. Dirac once fell asleep during someone else’s lecture, but woke during a moment when the speaker was getting stuck in a mathematical derivation, muttering: “Here is a minus sign where there should be a plus. I seem to have dropped a minus sign somewhere.” Dirac opened one eye and interjected: “Or an odd number of them.” One further example concerns a conference lecture he himself gave, following which a questioner indicated that he had not followed a particular part of Dirac’s argument. A long silence ensued, broken finally by the chairman asking if Professor Dirac would deal with the question. Dirac responded, “It was a statement, not a question.”

“Concepts in Thermal Physics” by J. Blundell and M. Blundell

Quotes

For his part, he insisted that the quantum world could not be expressed in words or imagined. To draw its picture would be “like a blind man sensing a snowflake. One touch and it's gone”. Its beauty revealed itself only in mathematical formulae.“The Strangest Man” by Graham Farmelo