Alan Mathison Turing





Alan Mathison Turing was born on June 23rd 1912 in London.  His father, Julius Mathison Turing, was a British civil servant in the Indian Civil Service.  His mother, Ethel Sara Stoney, was the daughter of a British official in India.  When Turing's mother joined her husband in India in 1913, Alan was left with family friends.  He was briefly sent to school, but did not begin school in earnest until he attended Hazlehurst Preparatory School.  Turing passed his Common Entrance Examination in 1926 and went to Sherborne, but his early schooling was not as stellar as one might expect from someone of his intellectual caliber, primarily because he seemed to pursue his own interests in his own fashion.  He nevertheless began a long string of mathematics prizes and awards a Sherborne.  He also excelled athletically, and is said to have been of nearly Olympic ability.   Hodges reports in Alan Turing : A Natural Philosopher (1997)  A note from Turing's headmaster at Sherborne:


If he is to stay at Public School, he must aim at becoming educated. If he is to be solely a Scientific Specialist, he is wasting his time at a Public School.


From 1928 to 1930 Turing found a friend and intellectual collaborator in Christopher Morcom.  Morcom's death in 1930 was difficult for Turing.  1931 found Turing beginning his career in mathematics at King's College, Cambridge University.  Turing had failed to win a scholarship in 1929, but took the scholarship examinations again in 1930 when he won a scholarship.  Cambridge proved a better atmosphere for Turing, though here too Turing spent a great deal of time reinventing and rediscovering in his own style.


Around 1933 Turing joined the anti-war movement developing in England in response to worries about Hilter's rise to power in Germany.  In 1934 graduated from Cambridge and was elected as a fellow of King's College in 1935.  Turing's election to King's was due to his dissertation.  In it Turing discusses Gaussian error functions and proved a number of results including the central limit theorem. Though the central limit theorem had already been proven by others, ex. by Andrei A Markov, Turing's proof was independent of their work of which he had no knowledge.  Also in 1935, Turing attended a course on the foundations of mathematics taught by Maxwell Newman, which exposed him to Gödel's incompleteness results and Hilbert's question on decidability. 


In April of 1936 Turing completed "On Computable Numbers, with an application to the Entscheidungsproblem," perhaps his most famous paper.  He showed it to Maxwell Newman and tried to publish it in the Proceedings of the London Mathematical Society.  However, Alonzo Church had proven such a result using the "lambda calculus" which he had invented a year earlier.  Church's paper, "An Unsolvable Problem of Elementary Number Theory," was published that very month in the American Journal of Mathematics.  The two proofs were quite different, particularly since Turing using the much more general approach of his now famous Turing Machines. Turing's paper is quite rich and also shows the existence of a Universal Turing Machine, .i.e., a general purpose computer. Turing's paper was accepted in August of 1936 with a reference to Church's paper.  


In a case of ideas being more important than accolades, Turing moved to Princeton where he studied with Church and Von Neuman and completed his Ph.D. in 1938.  Turing turned down a post at Princeton and returned to Cambridge.  Turing continued to publish papers in mathematics, but he was also recruited for the British Government Code and Cypher School at Bletchley Park, where he moved in 1939.  Turing working with W G Welchman developed the bombe, machines first developed by polish mathematicians, which greatly aided in cracking the coded messages sent and received by the German Luftwaffe.  The German Navel version of the cipher machine, Enigma, was considered unbreakable, but Turing's genius together with some lucky acquisitions of German information lead to these too being regularly decoded at Bletchley by 1941.  This work would occupy Turing through the end of the war.  However, by 1943 Turing was functioning largely as a consultant and worked at a different location on his own speech secrecy system.   


1945 found Turing working at London's National Physical Laboratory.  The publication by Eckert, Mauchly, and Von Neumann of their EDVAC resulted in Turing being named Senior Principal Scientific Officer to the project to build the Automatic Computing Engine, or ACE.  Turing's original design would have proven spectacular in comparison to other machines of the time.  However, worries by his colleagues about the engineering difficulties resulted in a more modest machine: The Pilot Model ACE.  Turing had actually left NPL in 1948 for Manchester University before the ACE machine was complete.  At Manchester Turing contributed to the development of the Mark I primarily by developing machine code programming.  In 1950 he wrote and published "Computing Machinery and Intelligence" in the philosophy journal Mind.  Turing increasingly turned his mind to Morphogenesis.  Fellowship of the Royal Society elected  him as a member in1951, mostly for his 1936 work.  Also in 1951 Turing submitted "The Chemical Basis of Morphogenesis"  which Hodges describes as "the founding paper of modern non-linear dynamical theory".  

In March of 1952 Turing was arrested for homosexuality.  He offered no denial or serious defense at his trial, as he had long been open about his sexuality and thought that he had done nothing wrong.  He was convicted on March 31st 1952, and opted for oestrogen injections (as opposed to a year in prison).  The conviction and resulting therapy must surely have been hard for Turing.  He was, for example, no longer eligible for a security clearance.  He was found dead on June 8th, 1954.  He had died on the 7th from potassium cyanide poisoning, which was found on a half eaten apple beside his bed.  The official ruling was suicide, however Turing was using the cyanide in experiments and no note was found.  His mother always maintained it was an accident.





Andrew Hodges Page on Turing Alan Turing Archive Tony Sales' Page on Codes and Ciphers
Turing Digital Archive Bletchley Park Page Virginia Tech's Biography
Cristian Cheran's Visual Turing Program Hobart and William Smith College Turing Applet Wallis Turing Machine Lab
Mactutor Biography Turing's Paper in Mind Stanford Encyclopedia Article