A Machine Made of Paper
Alan Turing was born in London in 1912 and raised at arm's length from parents stationed in colonial India, a solitary, shabby, brilliant boy whose schoolmasters despaired of his handwriting while he taught himself Einstein. The death at eighteen of Christopher Morcom, his first love and intellectual companion, marked him permanently and pushed his thinking toward the question of mind and mechanism. At Cambridge he became a King's College fellow at twenty-two, and in 1936 published the paper that founded computer science before computers existed.
On Computable Numbers imagined a strip of tape, a read-write head, and a table of rules, and proved that one such universal machine could execute any computation whatever, while some well-posed problems, the halting problem among them, no machine could ever decide. The abstraction, produced to settle a question in mathematical logic alongside Alonzo Church's independent work, is the blueprint under every processor on earth: hardware is one machine, software its interchangeable souls. He was twenty-three when he worked it out.
Hut 8
On the day after Britain declared war, Turing reported to Bletchley Park. Building on crucial foundations handed over by Polish cryptanalysts, Rejewski, Rozycki, and Zygalski, he designed, with Gordon Welchman's decisive refinement, the bombe: an electromechanical scythe that harvested German Enigma settings by the day. As head of Hut 8 he broke the U-boat ciphers upon which the Atlantic lifeline turned, and when bureaucracy starved the huts of typists and valves in 1941, he and colleagues wrote directly to Churchill, who ordered their needs met with extreme priority the same day.
Historians credit the Ultra intelligence stream with shortening the war in Europe by perhaps two or more years, arithmetic that translates into millions of lives; all of it remained secret for three decades, so the man who did it was publicly no one. Colleagues remembered the eccentrics' eccentric, jogging forty miles to London meetings, chaining his mug to the radiator, and being, in Joan Clarke's testimony, a kind and scrupulous friend; he proposed to her, disclosed his homosexuality, and remained her colleague after the engagement dissolved.
The Poisoned Apple
After the war he designed a complete electronic computer for the National Physical Laboratory, saw it built too slowly, and moved to Manchester, where the world's first stored-program machines were running. His 1950 paper Computing Machinery and Intelligence proposed the imitation game, judging machine thought by conversation, still the most famous thought experiment in artificial intelligence, and his 1952 work on morphogenesis used reaction-diffusion chemistry to explain how leopards get spots, founding a field biology took decades to catch up with.
In 1952, reporting a burglary by an acquaintance of a young man he was seeing, Turing candidly disclosed the relationship and was convicted of gross indecency. Offered prison or probation with hormone treatment, he accepted chemical castration, which deformed his body while he kept working. His security clearance vanished with the conviction. In June 1954 he was found dead of cyanide poisoning, a half-eaten apple beside him; the inquest ruled suicide, a verdict his mother and some later scholars have questioned as possibly accidental. A royal pardon came in 2013, a law bearing his name in 2017, and his face now looks out from the fifty-pound note.
