Turing was a hero of World War II, devising cryptanalytical techniques, including those that cracked the ENIGMA machine, helping the Allied war effort by enabling the reading of encrypted radio messages. This confirmed information provided by other sources and even yielded otherwise unavailable information (such as the real strength of German units, which could differ from Soviet and Anglo-American estimates). After the war Turing's work constituted the foundation of twentieth century computing (for the gory details see The Other Wiki's articles on Turing machines, undecidable problems and the Church-Turing thesis) .
In 1936, Turing went to Princeton University in America, returning to Britain in 1938. He began to work secretly part-time for the British cryptanalytic department, the Government Code and Cypher School. On the outbreak of war he took up full-time work at its headquarters, Bletchley Park.
Here he played a vital role in deciphering the messages encrypted by the German Enigma machine, which provided highly useful intelligence for the western Allies and - through official British communiques and Soviet spies - mildly useful information for the Soviets. He took the lead in a team that designed a machine known as a bombe that successfully decoded German messages. He became a well-known and rather eccentric figure at Bletchley.
A lesser-known fact about Turing is that he was also an accomplished physical athlete, a marathon-runner good enough to have had trials for the British Olympic team in 1948. This fed into his eccentricities: during the war he would sometimes travel from Bletchley to meetings in London by running. That's approximately 64 kilometers or 40 miles; a marathon and a half at least, and that assumes he never once took a wrong turn along the way - and many road signs were taken down as a precaution against invasion.
After the war, Turing turned his thoughts to the development of a machine that would logically process information. He worked first for the National Physical Laboratory (1945-1948). His plans were dismissed by his colleagues and the lab lost out on being the first to design a digital computer. It is thought that Turing's blueprint would have secured them the honour, as his machine was capable of computation speeds higher than the others. In 1949, he went to Manchester University where he directed the computing laboratory and developed a body of work that helped to form the basis for the field of artificial intelligence. In 1951 he was elected a fellow of the Royal Society.
In 1952, Turing was prosecuted for homosexuality, an imprisonable crime at the time, under the charge of Gross Indecency. Rather than face a prison sentence, Turing underwent chemical castration by the injection of synthetic oestrogen and lost his security clearance. He was barred from his previous position with GCHQ. In 1954, Turing was found dead; an autopsy showed the cause to be cyanide poisoning and it was ruled a suicide. Predictably speculation lingers on whether it was suicide, murder, or accident from sloppy chemical work, but the case is ambiguous enough for there to be significant doubt. Curiously a half-eaten apple was found at the scene but was never tested for poison. There is a story that the logo for Apple Computers was a reference to this apple, and thus to Alan Turing, but according to QI this just isn't true - although Apple did say they wished they had thought of it.
The British government in response to a successful petition officially apologized for the way he was treated in 2009, and he received a royal pardon on Christmas Eve, 2013. Very rare in the British justice system, which normally handles such cases by other means, this is only the fourth use of the royal prerogative of mercy granted since WWII. In 2017 this was extended to other men convicted under the law, who were retroactively pardoned, under a law popular known as the "Alan Turing Law." That many of the men pardoned thus were long-dead (among them Oscar Wilde) was seen as a Bittersweet Ending.
For Turing's proof of the undecidability of the Halting Problem, see this poem.
He will be featured on the £50 note beginning in 2021.
Media Featuring Alan Turing includes:
- Doctor Who Magazine features a robotic version of Turing as a major character in two separate stories: The Child of Time and The Phantom Piper.
- Über: Turing heads the team which decodes the secrets of making Ubers for the British, and even becomes a Tank-Man class Uber himself.
- In Atomic Robo, recent antagonist ALAN is a rogue artificial intelligence that evolved from Turing's work.
- The Imitation Game, a 2014 film starring Benedict Cumberbatch, which was somewhat controversial for its supposed downplaying of Turing's sexuality while exaggerating his eccentricity and for comments its star made about people on the autistic spectrum during the promotion of the film. The young Turing in flashbacks is played by Alex Lawther.
- Since the novel deals with decoding, James Bond appropriately meets young Turing in Double or Die when he goes to visit Cambridge. Turing turns up again in the epilogue, which is set near the end of World War II.
- Eighth Doctor Adventures, specifically The Turing Test, in which he is a major character and, at one point, the narrator. The book also features Joseph Heller and Graham Greene, and their (not very effusive) opinions on Turing as well as an amnesiac and exiled Eighth Doctor, with whom Turing develops something of a fascination and, eventually, an unrequited love.
- The Turing Option
- Cryptonomicon: Turing makes several appearances during the WW-2 portions of the book, as Lawrence Waterhouse's best friend.
- In The Laundry Files magic is done by solving certain types of math problems. Turing stumbled upon this when he solved the Turing / H. P. Lovecraft theorem. He was then Killed to Uphold the Masquerade by the eponymous Laundry, the British Men In Black who deal with the occult. The Laundry soon afterwards realized how bloody stupid they'd been, since they could have recruited Turing instead and reaped the benefits of his brilliance. Ever since they've made it their policy to recruit anyone who stumbles upon truth.
- He was the #21 "Greatest Briton" on One Hundred Greatest Britons.
- In Pennyworth, the character of Ian Thurso is an expy of Turing, being a genius British scientist who's persecuted for homosexuality.
- In the old World of Darkness, Turing was an early member of the Virtual Adepts. The Adepts claim he was assassinated by their enemies in the New World Order, while the NWO insists that Turing killed himself after being outed as gay. The setting leaves the issue hazy, potentially as a story hook.
- Breaking the Code, which was later adapted into a BBC TV movie in 1996
- Assassin's Creed: Brotherhood: A recorded Templar phone conversation between two Templars reveals that Turing was planning on creating robots using the Pieces of Eden, which they thought would threaten their plan for a New World Order by putting millions out of work. In response, they assassinated him with a poisoned apple to make it seem "poetic," since "Turing always theatrical."