Alan Turing

Their life

He defined computation itself before a single computer existed, broke naval Enigma at Bletchley Park, and asked 'can machines think?' — founding computer science and AI, before being persecuted by the country he helped save.

Known for

• The Turing machine and computability theory
• Breaking naval Enigma at Bletchley Park
• Founding theoretical computer science
• The Turing Test / 'Computing Machinery and Intelligence'
• Early work on mathematical biology and morphogenesis
• Conviction for 'gross indecency' and posthumous pardon

The road they walked

Alan Turing was born in London in 1912 into a family of colonial civil servants, the kind of English background that expected obedience and produced, in him, something closer to obsession. At Sherborne School he was an indifferent student except in mathematics, and he formed an intense friendship with a classmate, Christopher Morcom, whose sudden death in 1930 marked him deeply — some biographers trace his early interest in mind, matter, and what survives the body to that loss. At King's College, Cambridge, he found a place suited to his particular genius: solitary, exacting, unconcerned with convention. In 1936, still in his early twenties, he published 'On Computable Numbers,' which answered a deep question in mathematical logic by imagining an abstract machine reading and writing symbols on an infinite tape. The Turing machine was a thought experiment with no wires or vacuum tubes, but it defined, in principle, everything a computer could ever do — years before anyone built one.

The Second World War gave Turing's abstractions a body count attached to them. Recruited to the Government Code and Cypher School at Bletchley Park, he led the effort against German naval Enigma, a cipher the Royal Navy considered unbreakable, and his design for the electromechanical Bombe turned cryptanalysis into an industrial process. Historians estimate the intelligence from Bletchley shortened the war by roughly two years and saved millions of lives, though the work stayed classified for decades, so the public he'd helped protect knew nothing of it in his lifetime. After the war he moved between the National Physical Laboratory and the University of Manchester, sketching designs for stored-program computers and, in 1950, publishing 'Computing Machinery and Intelligence,' which posed the question 'can machines think?' and proposed the imitation game now known as the Turing Test. He also turned, in his final years, to biology, developing a mathematical theory of how patterns — stripes, spots, spirals — emerge in living things.

In 1952 Turing reported a burglary to the police and, in the course of the investigation, disclosed a sexual relationship with another man, Arnold Murray. Under British law at the time, this was a crime — 'gross indecency' — and he was convicted, stripped of his security clearance, and sentenced to a course of hormone treatment intended to suppress his libido, since chemical castration was offered as an alternative to prison. The conviction ended his access to the classified work that had defined his war, and by most accounts darkened the two years that remained to him.

How their story ended

Alan Turing died in June 1954 at his home in Wilmslow, Cheshire, found by his housekeeper with a half-eaten apple beside the bed and cyanide in his body. An inquest ruled the death suicide, and Turing had spoken to friends of the humiliations following his conviction. But the verdict has never been fully settled: he kept cyanide for chemical experiments in a makeshift home lab, the apple was never tested for poison, and some historians and family members have argued the death was accidental. He was 41. Britain issued a formal apology in 2009 and a royal pardon in 2013, and in 2017 the 'Alan Turing law' posthumously pardoned thousands of other men convicted under the same statute.

In their words

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Tables where Alan sits

The Machine Room

For computing’s founders — from the first program to the last bit.

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