Everything about Alan Turing totally explained
Alan Mathison Turing,
OBE,
FRS (
23 June 1912–
7 June 1954) was an
English mathematician,
logician and
cryptographer.
Turing is often considered to be the father of modern
computer science. Turing provided an influential formalisation of the concept of the
algorithm and computation with the
Turing machine. With the
Turing test, he made a significant and characteristically provocative contribution to the debate regarding
artificial intelligence: whether it'll ever be possible to say that a machine is
conscious and can
think. He later worked at the
National Physical Laboratory, creating one of the first designs for a stored-program computer, although it was never actually built. In 1948 he moved to the
University of Manchester to work on the
Manchester Mark I, then emerging as one of the world's earliest true computers.
During the
Second World War 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 that could find settings for the
Enigma machine.
Childhood and youth
Turing was conceived in
Chhatrapur,
Orissa,
India. His father, Julius Mathison Turing, was a member of the
Indian Civil Service. Julius and wife Sara (
née Stoney; 1881 – 1976, daughter of Edward Waller Stoney, chief engineer of the Madras Railways) wanted Alan to be brought up in
England, so they returned to
Maida Vale,
London, where Alan Turing was born
23 June 1912, as recorded by a
blue plaque on the outside of the building, now the
Colonnade Hotel. He had an elder brother, John. 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. Very early in life, Turing showed signs of the genius he was to display more prominently later.
His parents enrolled him at St Michael's, a day school, at the age of six. The headmistress recognised 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
General Strike in England, but so determined was he to attend his first day that he rode his bike unaccompanied more than from
Southampton to school, stopping overnight at an inn.
Turing's natural inclination toward mathematics and science didn't earn him respect with some of the teachers at Sherborne, a famous and expensive
public school, whose definition of education placed more emphasis on the
classics. His headmaster wrote to his parents: "I hope he won't fall between two schools. If he's to stay at public school, he must aim at becoming
educated. If he's to be solely a
Scientific Specialist, he's wasting his time at a public school".
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 16, 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.
Turing's hopes and ambitions at school were raised by the close friendship he developed with a slightly older fellow student, Christopher Morcom, who was Turing's first love interest. Morcom died suddenly 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's religious faith was shattered and he became an atheist. He adopted the conviction that all phenomena, including the workings of the human brain, must be materialistic.
University and his work on computability
Turing's unwillingness to work as hard on his classical studies as on science and mathematics meant he 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 there 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
central limit theorem.
In his momentous paper "On Computable Numbers, with an Application to the
Entscheidungsproblem" (submitted on
28 May 1936), Turing reformulated
Kurt Gödel's 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with what are now called
Turing machines, formal and simple devices. He proved that some such 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 practically realisable 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 isn't possible to decide, in general, algorithmically 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 can't 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, with Turing defending
formalism and Wittgenstein arguing that mathematics is overvalued and doesn't discover any absolute truths.
Cryptanalysis
During the
Second World War, Turing was a main participant in the efforts at
Bletchley Park to break German ciphers. Building on cryptanalysis work carried out in
Poland by
Marian Rejewski,
Jerzy Różycki and
Henryk Zygalski from
Cipher Bureau before the 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 (GCCS), the British code breaking organization. He worked on the problem of the German Enigma machine, and collaborated with
Dilly Knox, a senior GCCS codebreaker. On
4 September 1939, the day after Britain declared war on Germany, Turing reported to Bletchley Park, the wartime station of GCCS.
The Turing-Welchman bombe
Within weeks of arriving at Bletchley Park,
The bombe searched for possibly correct settings used for an Enigma message (ie, rotor order, rotor settings, etc), and used a suitable "
crib": a fragment of probable
plaintext. For each possible setting of the rotors (which had of the order of 10
19 states, or 10
22 for the U-Boat Enigmas which eventually had four rotors, compared to the usual Enigma variant's three), 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 mathematically 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 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 used in the Germans' new Geheimschreiber machine ("secret writer") which was one of those codenamed "Fish". He also introduced the Fish team to
Tommy Flowers who under the guidance of
Max Newman, went on to build the
Colossus computer, the world's first programmable digital electronic computer, which replaced simpler prior machines (including the "Heath Robinson") and whose superior speed allowed the brute-force decryption techniques to be applied usefully to the daily-changing cyphers. A frequent misconception is that Turing was a key figure in the design of Colossus; this wasn't the case.
Turing travelled to the United States in November 1942 and worked 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 officially 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, while teaching himself electronics at the same time, and assisted by engineer
Donald Bayley, Turing undertook the design of a portable machine codenamed
Delilah to allow
secure voice communications. It was intended for different applications, lacking capability for use with long-distance radio transmissions, and in any case Delilah was completed too late to be used during the war. Though Turing demonstrated it to officials by encrypting/decrypting a recording of a
Winston Churchill speech, Delilah wasn't adopted for use.
In 1945, Turing was awarded the
OBE for his wartime services, but his work remained secret for many years. A biography published by the Royal Society shortly after his death recorded:
» "Three remarkable papers written just before the war, on three diverse mathematical subjects, show the quality of the work that might have been produced if he'd settled down to work on some big problem at that critical time. For his work at the Foreign Office he was awarded the OBE."
Early computers and the Turing Test
From 1945 to 1947 he was at the
National Physical Laboratory, where he worked on the design of the
ACE (Automatic Computing Engine). He presented a paper on
19 February 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
10 May 1950.
In 1948 he was appointed Reader in the
Mathematics Department at
Manchester and in 1949 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". The idea was that a computer could be said to "think" if it could fool an interrogator into thinking that the conversation was with a human.
In 1948, Turing, working with his former undergraduate colleague,
D.G. Champernowne, began writing a chess program for a computer that didn't 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;
(External Link
) the program lost to Turing's colleague
Alick Glennie, although it's said that it won a game against Champernowne's wife.
Pattern formation and mathematical biology
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, putting forth the Turing hypothesis of pattern formation. 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.
Prosecution for homosexual acts and Turing's death
Turing was
homosexual, and at that time homosexuality was illegal in
Britain and regarded as a
mental illness and subject to criminal sanctions. In
1952, Arnold Murray, a 19-year-old recent acquaintance of his, 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 a crime having been identified and settled, they were charged with gross indecency under
Section 11 of the
Criminal Law Amendment Act of 1885. Turing was unrepentant and was convicted of the same crime
Oscar Wilde had been convicted of more than fifty years before.
He was given the choice between imprisonment and probation, conditional on his undergoing
hormonal treatment designed to reduce
libido. In order to avoid going to jail, he accepted the
estrogen hormone injections, which lasted for a year, with side effects including
gynecomastia (breast enlargement). His conviction led to a removal of his security clearance and prevented him from continuing consultancy for
GCHQ on cryptographic matters. At the time, there was acute public anxiety about spies and homosexual entrapment by Soviet agents.
On
8 June 1954, his cleaner found him dead; the previous day, he'd died of
cyanide poisoning, apparently from a cyanide-laced apple he left half-eaten beside his bed. 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. His mother, however, strenuously argued that the ingestion was accidental due to his careless storage of laboratory chemicals. Biographer Andrew Hodges suggests that Turing may have killed himself in this ambiguous way quite deliberately, to give his mother some
plausible deniability. Others suggest that Turing was reenacting a scene from "
Snow White", his favourite fairy tale. Because Turing's homosexuality would have been perceived as a security risk, the possibility of assassination has also been suggested. His remains were cremated at
Woking crematorium on
12 June 1954.
Posthumous recognition
Since 1966, the
Turing Award has been given annually by the
Association for Computing Machinery to a person for technical contributions to the computing community. It is widely considered to be the computing world's equivalent to the
Nobel Prize.
Various tributes to Turing have been made in Manchester, the city where he worked towards the end of his life. In 1994 a stretch of the A6010 road (the
Manchester city inner ring road) was named Alan Turing Way.
A
statue of Turing was unveiled in
Manchester on
23 June 2001. It is in
Sackville Park, between the
University of Manchester building on Whitworth Street and the
Canal Street '
gay village'. A celebration of Turing's life and achievements arranged by the
British Logic Colloquium and the
British Society for the History of Mathematics was held on
5 June 2004 at the
University of Manchester and the
Alan Turing Institute was initiated in the university that summer. The building housing the
School of Mathematics, the Photon Sciences Institute, and the
Jodrell Bank Centre for Astrophysics is named the
Alan Turing Building and was opened in July 2007.
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.
To mark the 50th anniversary of his death, a memorial plaque was unveiled on
7 June 2004 at his former residence, Hollymeade, in Wilmslow.
For his achievements in computing, various universities have honored him. On
28 October 2004 a bronze statue of Alan Turing sculpted by
John W Mills was unveiled at the
University of Surrey. The statue marks the 50th anniversary of Turing's death. It portrays Turing carrying his books across the campus. The
Polytechnic University of Puerto Rico and
Los Andes University in
Bogotá,
Colombia, both have computer laboratories named after Turing.
The
University of Texas at Austin has an honours computer science program named the
Turing Scholars.
Istanbul Bilgi University organizes an annual conference on the theory of computation called Turing Days. The computer room in
King's College, Cambridge is named the "Turing Room" after him.
Carnegie Mellon University has a granite bench, situated in The Hornbostel Mall, with the name "A. M. Turing" carved across the top, "Read" down the left leg, and "Write" down the other.
The
Boston GLBT pride organization named Turing their 2006 Honorary Grand Marshal.
A 1.5-ton, life-size statue of Turing was unveiled on
19 June 2007 at Bletchley Park. Built from approximately half a million pieces of Welsh
slate, it was sculpted by
Stephen Kettle, having been commissioned by the late American billionaire
Sidney Frank.
The Turing Relay is a six-stage relay race on riverside footpaths from
Ely to Cambridge and back to Ely. These paths were used for running by Turing while at Cambridge; his marathon best time was 2 hours, 46 minutes.
Experimental music duo
Matmos - the members of which are a homosexual couple - released a
limited edition EP in 2006 entitled
For Alan Turing.
Turing in fiction
Further Information
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