Alan Turing
Alan Mathison Turing,
OBE (
June 23,
1912 –
June 7,
1954) was an
English mathematician,
logician, and
cryptographer. Turing is often considered to be the father of modern
computer science.
With the
Turing test, Turing made a significant and characteristically provocative contribution to the debate regarding
artificial intelligence: whether it will ever be possible to say that a machine is
conscious and can
think. He provided an influential formalisation of the concept of
algorithm and computation with the
Turing machine, formulating the now widely accepted "Turing" version of the
Churchâ€"Turing thesis, namely that any practical computing model has either the equivalent or a subset of the capabilities of a Turing machine.During
World War II, Turing worked at
Bletchley Park, Britain's
codebreaking centre and was for a time head of
Hut 8, the section responsible for German Naval cryptanalysis. He devised a number of techniques for breaking German ciphers, including the method of the
bombe, an electromechanical machine which could find settings for the
Enigma machine.
After the war, he worked at the
National Physical Laboratory, creating one of the first designs for a stored-program computer, although it was never actually built. In 1947 he moved to the
University of Manchester to work, largely on software, on the
Manchester Mark I then emerging as one of the world's earliest true computers.
In 1952, Turing was convicted of acts of gross indecency after admitting to a sexual relationship with a man in
Manchester. He was placed on probation and required to undergo
hormone therapy. When Alan Turing died in 1954, an inquest found that he had committed
suicide by eating an apple laced with
cyanide.
Turing was conceived in 1911 in Chatrapur,
India. His father, Julius Mathison Turing, was a member of the
Indian civil service. Julius and wife Ethel (
née Stoney) wanted Alan to be brought up in
England, so they returned to
Paddington,
London, where Alan Turing was born June 23, 1912, as recorded by a
blue plaque on the outside of the building, now the Colonnade Hotel [
1]. His father's civil service commission was still active, and during Turing's childhood years his parents travelled between
Guildford,
England and
India, leaving their two sons to stay with friends in England, rather than risk their health in the British colony. Very early in life, Turing showed signs of the genius he was to display more prominently later. He is said to have taught himself to read in three weeks, and to have shown an early affinity for numbers and puzzles.
His parents enrolled him at St. Michael's, a day school, at the age of six. The headmistress recognized his genius early on, as did many of his subsequent educators. In 1926, at the age of 14, he went on to
Sherborne School in
Dorset. His first day of term coincided with a
general strike in England, and so determined was he to attend his first day that he rode his bike unaccompanied over sixty miles from
Southampton to school, stopping overnight at an
inn — a feat reported in the local press.
Turing's natural inclination toward mathematics and science did not earn him respect with the teachers at Sherborne, a famous and expensive
public school (a British private school with charitable status), whose definition of education placed more emphasis on the
classics. His headmaster wrote to his parents: "I hope he will not fall between two schools. If he is to stay at Public School, he must aim at becoming
educated. If he is to be solely a
Scientific Specialist, he is wasting his time at a Public School".
[Hodges, 1983, p. 26]Despite this, Turing continued to show remarkable ability in the studies he loved, solving advanced problems in 1927 without having even studied elementary
calculus. In 1928, aged sixteen, Turing encountered
Albert Einstein's work; not only did he grasp it, but he extrapolated Einstein's questioning of
Newton's laws of motion from a text in which this was never made explicit.
 |
The computer room at King's is now named after Turing, who became a student there in 1931 and a Fellow in 1935. |
Turing's hopes and ambitions at school were raised by his strong feelings for his friend Christopher Morcom, with whom he fell in love, though the feeling was not reciprocated. Morcom suddenly died only a few weeks into their last term at Sherborne, from complications of
bovine tuberculosis, contracted after drinking infected cow's milk as a boy. Turing was heart-broken.
Due to his unwillingness to work as hard on his classical studies as on science and mathematics, Turing failed to win a scholarship to
Trinity College, Cambridge, and went on to the college of his second choice,
King's College, Cambridge. He was an undergraduate from 1931 to 1934, graduating with a distinguished degree, and in 1935 was elected a Fellow at King's on the strength of a dissertation on the Gaussian
error function.
 |
Alan Turing, on the steps of the bus, with members of the Walton Athletic Club, 1946. |
In his momentous paper "On Computable Numbers, with an Application to the
Entscheidungsproblem" (submitted on
May 28,
1936), Turing reformulated
Kurt Gödel's 1931 results on the limits of proof and computation, substituting Gödel's universal arithmetics-based formal language by what are now called
Turing machines, formal and simple devices. He proved that such a machine would be capable of performing any conceivable mathematical problem if it were representable as an
algorithm, even if no actual Turing machine would be likely to have practical applications, being much slower than alternatives.
Turing machines are to this day the central object of study in
theory of computation. He went on to prove that there was no solution to the
Entscheidungsproblem by first showing that the
halting problem for Turing machines is
undecidable: it is not possible to algorithmically decide whether a given Turing machine will ever halt. While his proof was published subsequent to
Alonzo Church's equivalent proof in respect to his
lambda calculus, Turing's work is considerably more accessible and intuitive. It was also novel in its notion of a "Universal (Turing) Machine," the idea that such a machine could perform the tasks of any other machine. The paper also introduces the notion of
definable numbers.
Most of 1937 and 1938 he spent at
Princeton University, studying under Alonzo Church. In 1938 he obtained his
Ph.D. from Princeton; his dissertation introduced the notion of relative computing where Turing machines are augmented with so-called
oracles, allowing a study of problems that cannot be solved by a Turing machine.
Back in Cambridge in 1939, he attended lectures by
Ludwig Wittgenstein about the
foundations of mathematics. The two argued and disagreed vehemently, with Turing defending
formalism and Wittgenstein arguing that mathematics is overvalued and does not discover any absolute truths (Wittgenstein 1932/1976).
 |
Two cottages in the stable yard at Bletchley Park. Turing worked here from 1939â€"1940 until he moved to Hut 8. |
During
World War II, Turing was a major participant in the efforts at
Bletchley Park to break German ciphers. Building on cryptanalysis work carried out in Poland prior to the outbreak of war, he contributed several insights into breaking both the
Enigma machine and the
Lorenz SZ 40/42 (a teletype cipher attachment codenamed "Tunny" by the British), and was, for a time, head of Hut 8, the section responsible for reading German Naval signals.
Since September 1938, Turing had been working part-time for the
Government Code and Cypher School. Turing reported to
Bletchley Park on
4 September 1939, the day after Britain declared war on Germany.
[Copeland, 2006, p. 378]The Turing-Welchman bombe
 |
Replica of a bombe machine |
Within weeks of arriving at Bletchley Park,
Turing had devised an electromechanical machine which could help break Enigma: the
bombe, named after the Polish-designed
bomba. The bombe, with an enhancement suggested by mathematician
Gordon Welchman, became the primary tool used to read Enigma traffic.
The bombe searched for the correct settings of the Enigma rotors, and required a suitable "
crib": a piece of matching
plaintext and
ciphertext. For each possible setting of the rotors, the bombe performed a chain of logical deductions based on the crib, implemented electrically. The bombe detected when a contradiction had occurred, and ruled out that setting, moving onto the next. Most of the possible settings would cause contradictions and be discarded, leaving only a few to be investigated in detail. Turing's bombe was first installed on
18 March 1940. Over 200 bombes were in operation by the end of the war.
Hut 8 and Naval Enigma
In December 1940, Turing solved the naval Enigma indicator system, which was more complex than the indicator systems used by the other services. Turing also invented a
Bayesian statistical technique termed "
Banburismus" to assist in breaking Naval Enigma. Banburismus could rule out certain orders of the Enigma rotors, reducing time needed to test settings on the bombes.
In the spring of 1941, Turing proposed marriage to fellow Hut 8 co-worker
Joan Clarke, although the engagement was broken off by mutual agreement in the summer.
In July 1942, Turing devised a technique termed
Turingismus or
Turingery for use against the Lorenz cipher. A frequent misconception is that Turing was a key figure in the design of the
Colossus computer; this was not the case.
[Copeland, 2006, pp. 382-383]Turing travelled to the United States in November 1942 and liaised with US Navy cryptanalysts on Naval Enigma and bombe construction in Washington, and assisted at
Bell Labs with the development of
secure speech devices. He returned to Bletchley Park in March 1943. During his absence,
Hugh Alexander had assumed the position of head of Hut 8, although Alexander had been
de facto head for some time, Turing having little interest in the day-to-day running of the section. Turing became a general consultant for cryptanalysis at Bletchley Park.
In the latter part of the war, teaching himself electronics at the same time, Turing undertook (assisted by engineer
Donald Bayley) the design of a portable machine codenamed
Delilah to allow
secure voice communications. Intended for different applications, Delilah lacked capability for use with long-distance radio transmissions, and was completed too late to be used in the war. Though Turing demonstrated it to officials by encrypting/decrypting a recording of a
Winston Churchill speech, Delilah was not adopted for use.
In 1945, Turing was awarded the
OBE for his wartime services.
 |
Turing achieved world-class Marathon standards. His best time of 2 hours, 46 minutes, 3 seconds, was only 11 minutes slower than the winner in the 1948 Olympic Games. |
From 1945 to 1947 he was at the
National Physical Laboratory, where he worked on the design of
ACE (Automatic Computing Engine). He presented a paper on February 19, 1946, which was the first complete design of a
stored-program computer in Britain. Although he succeeded in designing the ACE, there were delays in starting the project and he became disillusioned. In late 1947 he returned to Cambridge for a 'sabbatical' year. While he was at Cambridge, ACE was completed in his absence and executed its first program on May 10, 1950. In 1949 he became deputy director of the computing laboratory at the
University of Manchester, and worked on software for one of the earliest true computers — the
Manchester Mark I. During this time he continued to do more abstract work, and in "
Computing machinery and intelligence" (Mind, October 1950), Turing addressed the problem of
artificial intelligence, and proposed an experiment now known as the
Turing test, an attempt to define a standard for a machine to be called "sentient".
In 1948, Turing, working with his former undergraduate colleague,
D.G. Champernowne, began writing a chess program for a computer that did not yet exist. In 1952, lacking a computer powerful enough to execute the program, Turing played a game in which he simulated the computer, taking about half an hour per move.
The game was recorded; the program lost to a colleague of Turing,
Alick Glennie, however, it is said that the program won a game against Champernowne's wife.
Turing worked from 1952 until his death in 1954 on
mathematical biology, specifically
morphogenesis. He published one paper on the subject called "The Chemical Basis of Morphogenesis" in 1952. His central interest in the field was understanding
Fibonacci phyllotaxis, the existence of
Fibonacci numbers in plant structures. He used reaction-diffusion equations which are now central to the field of
pattern formation. Later papers went unpublished until 1992 when
Collected Works of A.M. Turing was published.
Turing was a homosexual during a period when homosexual acts were illegal and homosexuality was regarded as a mental illness. In 1952, Arnold Murray, a 19 year old recent acquaintance of his (cf. Hodges' book pp.449-455) helped an accomplice to break into Turing's house, and Turing went to the police to report the crime. As a result of the police investigation, Turing acknowledged a sexual relationship with Murray, and they were charged with gross indecency under
Section 11 of the Criminal Law Amendment Act of 1885. Turing was unrepentant and was convicted. He was given the choice between imprisonment and probation, conditional on him undergoing
hormonal treatment designed to reduce
libido. In order to avoid going to jail, he accepted the
oestrogen hormone injections, which lasted for a year, with side effects including the
development of breasts. His conviction led to a removal of his security clearance and prevented him from continuing consultancy for
GCHQ on cryptographic matters.
In 1954, he died of
cyanide poisoning, apparently from a cyanide-laced apple he left half-eaten. The apple itself was never tested for contamination with cyanide, and cyanide poisoning as a cause of death was established by a post-mortem. Most believe that his death was intentional, and the death was ruled a
suicide. It is rumoured that this method of self-poisoning was in tribute to Turing's beloved film
Snow White and the Seven Dwarfs. His mother, however, strenuously argued that the ingestion was accidental due to his careless storage of laboratory chemicals. Friends of his have said that Turing may have killed himself in this ambiguous way quite deliberately, to give his mother some plausible deniability. The possibility of assassination has also been suggested, owing to Turing's involvement in the secret service and the perception of Turing as a security risk due to his homosexuality.
In the book,
Zeroes and Ones, author
Sadie Plant speculates that the
rainbow Apple logo with a bite taken out of it was an homage to Turing. This is unlikely as Gilbert Baker's
rainbow pride flag, a
gay pride emblem, was designed two years after the Apple logo, thus negating the possibility of it referring to Turing's sexuality.
Since 1966, the
Turing Award has been given by the
Association for Computing Machinery to a person for technical contributions to the computing community. It is widely considered to be the equivalent of the
Nobel Prize in the computing world.
In 1994 a stretch of the
Manchester city inner ring road was named Alan Turing Way.
On
23 June 1998, on what would have been Turing's 86th birthday,
Andrew Hodges, his biographer, unveiled an official
English Heritage Blue Plaque on his childhood home in Warrington Crescent,
London, now the Colonnade hotel [
2], [
3].
 |
Alan Turing memorial statue in Sackville Park |
A
statue of Turing was unveiled in
Manchesteron
June 23 2001. It is in
Sackville Park, between the
University of Manchester building on Whitworth Street and the
Canal Street '
gay village'. To mark the 50th anniversary of his death, a memorial plaque was unveiled at his former residence, Hollymeade, in Wilmslow on
June 7 2004.
 |
Plaque marking Turing's home |
The
Alan Turing Institute was initiated by
UMIST and
University of Manchester in Summer 2004.
A celebration of Turing's life and achievements was held at the
University of Manchester on
5 June 2004; it was arranged by the
British Logic Colloquium and the
British Society for the History of Mathematics.
On
October 28 2004 a bronze statue of Alan Turing sculpted by
John W. Mills was unveiled at the
University of Surrey [
4]. The statue marks the 50th anniversary of Turing's death. It portrays Turing carrying his books across the campus.
Holtsoft produces a
programming language named for Turing. The language is designed for beginner programmers and has no direct access to the hardware.
The
Polytechnic University of Puerto Rico named a computer laboratory for graduate studies the
Turing Lab.
The
University of Texas at Austin has an honours computer science program named the
Turing Scholars.
The
Plymouth State University of
New Hampshire has named the server used by the computer science department after Turing.
The
Boston GLBT pride organization, http://www.bostonpride.org/, named Turing their 2006
Honorary Grand MarshalIstanbul Bilgi University organizes an annual conference on the theory of computation called
Turing Days. Carnegie Mellon University has a granite bench, situated in The Hornbostel Mall, with the name "Alan Turing" carved across the top, "Read" down the left leg, and "Write" down the other.
* Turing's mother, Sara Turing, who survived him by many years, wrote a biography of her son.
* Andrew Hodges wrote a definitive biography
Alan Turing: The Enigma in 1983 (see references below).
* The play
Breaking the Code by Hugh Whitemore is about the life and death of Turing. In the original
West End and
Broadway runs, the role of Turing was played by
Derek Jacobi, who also played Turing in a 1995 television adaptation of the play.
*
* Bodanis, David.
Electric Universe: How Electricity Switched on the Modern World. New York: Three Rivers Press, 2005. ISBN 0307335984
* Turing appears as a character in
Neal Stephenson's
Cryptonomicon.
* In another one of Stephenson's books,
The Diamond Age, there is an intuitive explanation of recursion, important to Turing's and related work on computability, put into the format of a child's book.
* An
FBI agent named Alan Turing made an appearance in the
webcomic Questionable Content as a homage to Turing.
* Mentioned in
Enigma by
Robert Harris, but never enters the narrative of the book.
* A young Alan Turing introduces the title character to
Gödel's first
incompleteness theorem in
Apostolos Doxiadis's novel
Uncle Petros and Goldbach's Conjecture.
* In the 1989
Doctor Who serial
The Curse of Fenric, the character of Dr. Judson is based on Turing. Turing himself is a narrator of the
Doctor Who spin-off novel The Turing Test by Paul Leonard.
*
Greg Egan's novella,
Oracle, is about an alternate universe version of Turing
* In
Arthur C. Clarke's
2010: Odyssey Two, the sequel to
2001: A Space Odyssey, the stoic
Dr. Chandra, the programmer who created
HAL 9000, has a completely spartan cubicle except for photos of Turing and
John von Neumann beside his blackboard.
* In
John Banville's
The Untouchable, the character Alastair Sykes is modeled on Alan Turing.
* In the novel
Neuromancer by
William Gibson, there is a police force called the
Turing Police designed to crack down on computers acquiring too much intelligence.
*
List of gay, lesbian or bisexual people*
Alan Turing's Unorganized Machines*
*
B. Jack Copeland, (2004) "Colossus: Its Origins and Originators".
IEEE Annals of the History of Computing, 26(4):38–45.
* B. Jack Copeland, (editor, 2004)
The Essential Turing.
Oxford University Press, ISBN 0-19-825079-7 (hardback) and ISBN 0-19-825080-0 (paperback).
* B. Jack Copeland, (editor, 2005),
Alan Turing's Automatic Computing Engine.
Oxford University Press, ISBN 0-19-856593-3.
* B. Jack Copeland (editor, 2006),
Colossus: The Secrets of Bletchley Park's Codebreaking Computers, 2006, Oxford University Press, ISBN 019284055X.
*
Andrew Hodges, (1983/2000).
Alan Turing: The Enigma.
Simon & Schuster, 1983, ISBN 0-671-49207-1. Also: Walker Publishing Company, 2000.
*
Christof Teuscher (editor 2004),
Alan Turing: Life and Legacy of a Great Thinker.
Springer-Verlag, ISBN 3540200207.
* David M. Yates, (1997)
Turing's Legacy: A history of computing at the National Physical Laboratory 1945â€"1995. London:
Science Museum, ISBN 0-901805-94-7.
*
Ludwig Wittgenstein (1932/1976)
Wittgenstein's Lectures on the Foundations of Mathematics (1932â€"1935). Edited by Cora Diamond. Cornell University Press.
*
Johnson, George (2005) "Enigmatic". New York Times Book Review (12/18/2005). Review of David Leavitt,
The Man Who Knew Too Much: Alan Turing and the Invention of the Computer (2005).
*
Holt, Jim (2006) "CODE-BREAKER The life and death of Alan Turing.". The New Yorker (1/30/2006). Review of David Leavitt,
The Man Who Knew Too Much: Alan Turing and the Invention of the Computer (2005).
*
Alan Turing Home Page by Andrew Hodges including a
short biography*
AlanTuring.net Turing Archive for the History of Computing by Jack Copeland
*
A short biography*
Alan Turing – Towards a Digital Mind: Part 1*
Computing machinery and intelligence — full text of article.
*
Hollymeade unveiling of memorial plaque marking 50th anniversary of Turing's untimely death*
Alan Turing and morphogenesis*
The Turing Archive*
Turing Day 2002*
Turing 2004: A celebration of his life and achievements*
Stanford Encyclopedia of Philosophy entry*
Turing Days*
Photos*
Online version of Turing's paper On Computable Numbers, With An Application To The Entscheidungsproblem (Requires Microsoft Internet Explorer 5.5 or above - special characters rendered incorrectly on other browsers)
*
Time 100:Alan Turing*
Morton, Paul Econoculture Interview with David Leavitt about The Man Who Knew Too Much: Alan Turing and the Invention of the Computer February 2 2006
