During Alan Turing Year celebrations are being held all over the world; many in places Turing himself never visited. He did, however, spend two years at Princeton University which has just held a three-day conference to mark its association with Turing.
In 2008 Alan Turing was voted as the second most influential Princetonian in its history - top pf the poll was James Madison, Princeton's first graduate student in 1771 and President of the USA from 1809-1817. Turing was at Princeton for two years from 1936 and didn't really fit in. He wrote to his mother that it was hard to be recognized when Einstein and von Neumann were just down the hall.
Once he had gained his PhD with the dissertation Systems of Logic Based On Ordinals, von Neumann offered Turing a position at the Institute for Advanced Study to continue his mathematical research but he preferred to return to England.
This image, the logo for the Turing Centennial Celebration website, uses the photo from Turing's Graduate School File and is composed from portions of his PhD dissertation.
So how had it come about that Turing, who was a loner and shy to the point of being a social misfit, had arrived at Princeton where he found himself in such elevated company?
As a graduate student at Cambridge University, Turing wrote his seminal paper On computable numbers, in which he documented his idea of the Turing machine, without ever being aware that the same topic, proving the undecidability of whether a statement in first-order logic is a theorem, the Entscheidungsproblem, had been tackled by Alonzo Church. Church's proof, first presented in 1935 before the American Mathematical Society and then published in the Journal of Symbolic Logic, used lambda calculus as system of computation, but used a similar technique of diagonalization as Turing employed with regard to his machines.
Max Newman, Turing's supervisor at Cambridge, wrote to Church telling him of Turing's work:
"His treatment, which consists in describing a machine which will grind out any computable sequence- is rather different from yours, but seems to be of great merit, and I think it of great importance that he should come and work with you next year if that is at all possible.”
Turing was one of Church's graduate students in the Department of Mathematics. During his two-year stay not only did he complete his PhD dissertation, he wrote a paper on lambda calculus, two papers on group theory and an addition to On Computable Numbers which mapped his work to that of Church. However, apart from Von Neumann few people seemed to take notice of him.
According to an account by Jon Edwards, co-coordinator of the Princeton Turing Centennial Celebration:
Ever humble and evidently inept at self-promotion, his Princeton talk about the Turing machine was sparsely attended. He received only two requests for reprints for his paper. Few of his colleagues seemed patient enough to dig into his complex arguments. And as Turing himself put it in a note home to his mother, solving the entsheidungsproblem not so much a big deal when Einstein was just down the hall.
Edwards also notes that Church appeared not to count Turing as one of his students, stating in an interview in 1984:
Well, he was at Princeton, but not only under my supervision, because, of course, he had worked with M.H.A. Newman in England. It was while he was working with Newman that his truly original ideas came out.
However, with hindsight Princeton now counts Alan Turing as one of its prestigious alumni and has mounted a series of events to mark the association.
Celebrations commenced in April when Turing biographer, Professor Andrew Hodges from Oxford University delivered a lecture, Alan Turing: An Atlantic Perspective:
Princeton University Press has also published a centenary US edition of Andrew Hodges book, Alan Turing: The Enigma, see sidebar.
The other book to come out for the centenary celebration is Alan Turing's Systems of Logic: The Princeton Thesis, a reproduction and an examination of Turing's Princeton dissertation with essays from Solomon Feferman and Andrew Appel.
Andrew Appel has also made a short video, Turing's Legacy to Computer Science at Princeton:
In the video Appel, who is the current Professor of Computer Science at Princeton says:
One could say that the greatest computer science departmnet in the world in the 1930s was the Princeton Math department because Church's lambda calculus became the prototype of the programming languages that we use; Turing's machine became the prototype of the computers developed by John von Neumann at the Institute for Advanced Study in Princeton in which the program is just stored as data in the memory of the computer.
Turing's legacy, as well as the future of computing was discussed at the Princeton Turing Centennial Conference where speakers included eight winners of the Turing Award. Google CEO Eric Schmidt gave the Public Address and his talk was recorded in its entirety:
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