Alan Turing by Jim Eldridge

Alan Turing by Jim Eldridge

Author:Jim Eldridge
Language: eng
Format: epub
Publisher: Bloomsbury Publishing
Published: 2013-12-21T05:00:00+00:00


9

Return to Britain

In March 1943, Alan returned to Britain on a troopship. Again, he was lucky it wasn’t a target for German U-boats. Possibly he trusted in the fact that by now his colleagues in Hut 8 at Bletchley Park, thanks to the cracking of the Enigma code, had German U-boat movements in the Atlantic under some sort of control.

In his absence, Hugh Alexander, Alan’s code-breaking colleague and one of the co-signatories of the letter to Churchill, had taken over the leadership of Hut 8, continuing the work of code-breaking the German naval Enigma. As Alan soon realised, the code-breaking work of Hut 8 was proceeding well, with the Enigma codes being broken and the German’s secret messages being read successfully and regularly. To a great extent, Alan was no longer vital to the work of Hut 8.

The commanders at Bletchley Park offered Alan a new code-breaking challenge instead. The Germans were using another code, this one produced by the German Lorenz machine, which the British called Fish. (Tunny was one of the codes produced by this system.) To break this code, a team had designed and built an electronic machine, which they called Heath Robinson, which used two paper tapes. The first tape had on it coded characters from an intercepted message; the other tape had possible wheel patterns from the Lorenz code machine. The paper tape ran through the machine at a thousand characters a second. The main problems with this machine were that the paper tapes often got out of sync, and that the paper often snapped.

Max Newman, one of Alan’s former tutors at Cambridge, had looked at the problems affecting the Heath Robinson machine, and he and an electronics engineer called Tommy Flowers had designed and built their own version of the machine, which used patterns generated electronically rather than paper tape. Because of this it was able to process five thousand characters a second. Newman and Flowers called their machine Colossus. It was one of the very first digital electronic computers. Newman invited Alan to join him and Flowers to develop Colossus and give it even greater ability.

Alan declined. The research he had been exposed to in America, particularly the voice encryption work at Bell Labs, inspired him to want to develop a machine that not only had the power of independent thought and decision-making – his Thinking Machine – but one that would be able to communicate using speech. If this could be done and the coded message could be simply listened to as real human speech, then the long job of translating a physical code, letter by letter, as had previously been the case, would be unnecessary.

* * *

Meanwhile, what of Joan Clarke? When Alan had left for America the previous November, there was an understanding between them that they were engaged, and would be married. But perhaps their time apart had given them both time to think about what such a marriage might mean for them, especially in view of Alan’s admission to being gay.



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