Seeing History
Alan Turing

Turing (1912-1954) was one of the most original mathematical minds of the 20th century. Not being classically inclined, he failed to win a scholarship at his "public school" and went to King's College instead, where he graduated with honors in 1934. He became a Fellow of King's in 1935. His profoundly important paper "On Computable Numbers" (1936) is regarded as a keystone of the thinking that led to the computer. Turing got his PhD from Princeton in 1938. In the fall of that year he was drawn into the British intelligence effort in what was already shaping up as World War Two.

Britain declared war on Germany on 3 September 1939. On 4 September, Turing reported to Bletchley Park, the secret center of that effort. He was first housed in an apartment in the mansion's former stable, and later put in charge of Hut 8, where work on German naval codes was concentrated. Turing quickly mapped out what would be required to consider and reject impossible settings for the German "Enigma" machine on which certain decrypted messages had been encoded. The first such decoding machine, called a "bombe," was installed on 18 March 1940. Hundreds of them were eventually in operation. In December 1940, he made further progress with the German Enigma machine, and in July 1942 succeeded in cracking a different German cipher. In 1942 he introduced Tommy Flowers to his team; Flowers (not Turing himself, as is often said) went on to design the more sophisticated Colossus computer. From November 1942 to March 1943 he served in the United States, as part of the coordination of intelligence services between the two allies, also working with Bell Labs on secure speech communication.

Early in December 1943, the first successful prototype of the decrypting computer "Colossus" was disassembled for shipment to Bletchley Park. It was first put into operation in January 1944, and was successful on that occasion. Its use helped to turn aside a renewed German submarine warfare initiative, and solidified Allied control of the Atlantic, as a precondition for the Normandy invasion of June 1944.

Colossus used rapid optical input (5,000 characters per second; the paper tape feed is visible in the picture) as well as extremely sophisticated decrypting circuitry, applied thousands of times to the message once input. It was by far the most advanced thing of its kind at the time. (Its nearest American counterpart, the ENIAC fast arithmetic machine, which was intended for the computation of artillery tables, did not become operational until 1946, too late to play a part in the intelligence wars). Ten Colossus machines were built for Bletchley Park. Eight were destroyed at war's end in August 1945, and the remaining two in the 1960's. Their progeny are everywhere, including the thing which is sitting in front of you as you read this.

After the war, to which his secret contribution of necessity remain secret for many years, Turing continued with pioneer work on computers, including a paper of February 1946 which gave the design for a stored-program computer. This was built under his direction at the National Physical Laboratory, but there were difficulties in its becoming operational, and like the late fruits of his early Bletchly efforts, the machine came into operation only after he had moved on to something else: a sabbatical at Cambridge. He later headed the computational lab at Manchester University. Artificial intelligence, a chess playing program (which in simulated form was successful against weak opponents), and mathematical biology (the occurrence of Fibonacci patterns in biological forms; again, the sense of the pattern in the data), were some of his interests at the end. A similar theoretical reach and grasp are visible, even to ordinary minds, in these fields which engaged the attention of Turing's mind.

No one who reads this page is likely to go out and do these things, or any others remotely comparable. But it is good to know that such things exist, and can occasionally be done, when the chances of war and natural endowment happen to exist in a particularly favorable conjunction.

17 Dec 2006 / Contact The Project / Exit to Outline Index Page