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Remembering Alan Turing

I was recently in Cambridge—not the big one with Harvard and MIT and all that, but the small market town in England. It would be an unvisited East Anglian backwater today if a few scholars had not started a small university there about 800 years ago. Today it is one of the best in the world, boasting alumni like Isaac Newton, Francis Bacon, Lord Byron, Charles Darwin, Charles Babbage, John Maynard Keynes, David Attenborough, Jane Goodall, and the current heir to the UK throne.

On June 21 a friend and I took a lazy guided boat tour past a few of the colleges, and the guide mentioned several of the above-named alumni; but we noticed one name that was missing. In 48 hours it would be June 23, 2012: the 100th birthday of Alan Turing. (Sadly, Turing did not live to see even his 50th. In 1952 his honesty and integrity led him to acknowledge when talking to the police that a young man who stole from him had been a sexual partner. The police ignored the thief and prosecuted Turing instead. He was convicted and subjected to an unpleasant chemical castration, and was found dead of cyanide poisoning in June 1954.)

We pointed out to our gondolier that, in this week especially, Turing’s name should be mentioned when passing the back of King’s College. And the young man—paid to give tour-guide speeches about the various claims to fame of Cambridge University—told us he had never heard of Turing!

Gulp. One struggles not to seem like an Old Guy muttering into his beard about Youth Today, but really. The world is utterly different because of Turing. World War II might not have been won without his code-breaking work at Bletchley Park.* Computers in their modern form were first conceived when his mathematical mind led him to think about what it meant for a problem to be solvable by an exact procedure. It seemed shocking that in 2012 a student guiding a punt past King’s hadn’t even heard of him.

Honoring Turing was the whole reason for my visit. I was at the 2012 Computability in Europe meeting (CiE), which was devoted to commemorating the Turing centenary. I heard many fascinating papers about Turing’s life and work. His insights lie at the origin of half a dozen areas of a research: logic and mathematics (“On Computable Numbers”); chemistry and biology (“The Chemical Basis of Morphogenesis”); the philosophy of artificial intelligence (“Computing Machinery and Intelligence”); and statistics and cryptography (a great deal of his work in those fields being unpublishable because of wartime secrecy).

And I’m not even counting computer science here, because he couldn’t contribute to that: It didn’t exist until it grew out of his 1936 paper.

“On Computable Numbers” established the theoretical foundations for the idea of a universal computing machine that could run any program you might supply. It also founded the subfield of computer science devoted to studying literally unsolvable computational problems. Turing actually exhibited one: The “halting problem” for what are now called Turing machines (Will the program P eventually stop if it is given the data D as its input?) has no general computational solution method. A large part of the work that the theorists at CiE meetings do is devoted to the further development of this mathematical point.

The organizers of the conference allowed me the great privilege of doing a short presentation at the final session. I read to the assembled computer scientists in the Babbage Lecture Theatre my poem, “Scooping the Loop Snooper,” which restates the proof of the undecidability of the halting problem in Dr. Seuss-like verse. I never had so much fun in my life. A hall packed with people who understood the proof but had enough of a sense of humor to roar with laughter. It was a great success. I very much hope that Alan Turing (who definitely had a boyish sense of fun) would have appreciated it as a birthday surprise. And I weep when I think of how he could have lived into old age rather than be hounded to death by 1950s criminalization of gay sexuality. He should have been made a peer of the realm; Lord Turing of Bletchley, perhaps. Happy 100th birthday, Alan.


*Update June 28, 3:30 p.m.: The standard story places Turing in the forefront of the Bletchley Park codebreaking heroes, and indeed Turing was an intellectual leader in the machine design work, and was entrusted with important roles such as traveling to the USA to liaise with the Americans about ramping up the cryptanalytical effort. But of course Bletchley Park was not just Alan Turing alone in a hut. See Michael Saunders’ June 27 letter to The Guardian, which points out inter alia that the Poles made important contributions before the British even got started, and that we should not overlook “the 9,000 other staff, two-thirds women, who also served at Bletchley Park.”

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