Alan Turing

Alan Mathison Turing (June 23,1912-June 7,1954), British mathematician and computer scientist ante litteram, considered to be one of the fathers of modern digital computing. In his paper "On Computable Numbers, with an Application to the Entscheidungsproblem" (1936), he proved that there was no solution to the Entscheidungsproblem by first showing that the halting problem for Turing machines (a formal device introduced by Turing and useful in computational theory) is unsolvable. While his proof was published subsequent to that of Alonso Church, Turing's work is considerably more accessible and intuitive.

He was a major participant in the code breaking efforts at Bletchley Park during World War II on cracking Nazi Enigma ciphers. He contributed several mathematical insights, both to breaking the Engima code and the Fish teletype cyphers (machines made by both Lorenz and Siemens). The Fish insights were useful in the development of the special-purpose digital computer Colossus, which was developed by Max Newman and built at the Post Office Research Station at Dollis Hill by a team led by Thomas Flowers in 1943 and used to crack Fish cyphers. Turing also designed advanced versions of the Polish "bombe" used to assist in finding keys for Enigma messges. These were electromechanical devices coupling several 'Enigma machines' which were able to eliminate at high speed large numbers of possible key settings for blocks of Enigma traffic.

In "Computing Machinery and Intelligence," (Mind, October 1950) Turing tackled the problem of artificial intelligence, and proposed an experiment now known as the Turing Test, a standard for an intelligent machines which is the focus of the Loebner Prize.

In 1952 his lover helped a compatriot to break into his house and commit larceny. Turing went to the police to report the crime. As a result of the police investigation, he was charged with homosexuality ("gross indecency and sexual perversion"), unapologetically offered no defense, and was convicted. Following the well-publicized trial, he was given a choice between incarceration and libido-reducing hormonal treatment. He chose the hormone injections, which lasted for a year, with side effects including the development of breasts during that period. In 1954 he almost certainly committed suicide by eating a cyanide-laced apple.