## Alan Turing Essay Writing Contest: Runners-Up, Ayushi Dalmia

Posted on April 16, 2012

**Alan Turing:The Enigma**

“A computer would deserve to be called intelligent if it could deceive a human into believing that it was human.” –Alan Turing

Alan Mathison Turing was born on 23^{rd} June,1912. The American Mathematical Society considers his birth as one of the great events in the history of Mathematics. His father, Julius Mathison Turing, was a member of the Indian Civil Service. Alan and his elder brother John did not see much of their parents, who were in India, and were fostered in various English homes where nothing encouraged expression, originality, or discovery. Science for him was an extra-curricular passion. He dreamed his way through, doing chemistry experiments of his own. In the midst of the General Strike of 1926, Turing started at Sherborne School. But his natural inclination towards mathematics and Science did not earn him respect. The headmaster soon wrote to his parents:

“I hope he will not fall between two stools. 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”

After Sherborne, Turing went to study at King’s College, Cambridge. He was an undergraduate there from 1931 to 1934, graduating with first-class honours in Mathematics. In 1935, at the young age of 22, he received a fellowship from King’s College.

In 1935, Turing learnt from the lecture course of the Cambridge topologist M. H. A. Newman that a question, posed by Hilbert, still lay open. It was the Question of Decidability, the *Entscheidungsproblem.* Could there exist, at least in principle, a definite method or process by which it could be decided whether any given mathematical assertion was provable? People had already used the concept of a ‘mechanical’ process, and Turing had an idea which made this quite precise: computability.

Turing wrote in his first sentences:

The “computable” numbers may be described briefly as the real numbers whose expressions as a decimal are calculable by finite means… a number is computable if its decimal can be written down by a machine.

Having made this novel definition of what should count as a ‘definite method’ — in modern language, an algorithm — it was not too hard to answer Hilbert’s question in the negative: no such decision procedure exists. Subsequently, the concept of the Turing machine has become the foundation of the modern theory of computation and computability. His work introduced a concept of immense practical significance: the idea of the Universal Turing Machine.

In 1938 Turing was offered a temporary post at Princeton by von Neumann but instead returned to Cambridge. Secretly, he was working part-time for the British cryptanalytic department, the so-called Government Code and Cypher School. After Britain’s declaration of war on 3 September, Turing took up full-time work at the wartime cryptanalytic headquarters, Bletchley Park. He along with Dilly Knox started to work on a less fragile problem to decrypt Enigma messages and produced the initial functional specification of the bombe. The bombe, with an enhancement suggested by mathematician Gordon Welchman, became one of the primary tools, and the major automated one, used to attack Enigma-enciphered messages.

In contrast, the more complex Enigma methods used in German Naval communications were generally regarded as unbreakable. In December 1939, Turing solved the essential part of the naval indicator system.

After working at the Bell Labs on the development of SIGSALY, a secure voice system and at National Physics laboratory where he worked on the design of ACE (Automatic Computing Engine),he was appointed as a Reader in the Mathematics Department in the University of Michigan. Later he devoted his time to the problem of artificial intelligence and designed the Turing Test. The idea was that a computer could be said to “think” if a human interrogator could not tell it apart, through conversation, from a human being. He also invented the famous LU Decomposition which is used today for solving equations in matrix.

In 1952,Turing shifted his attention to mathematical biology, specially morphogenesis. He set as a particular goal the explanation for the appearance of the Fibonacci numbers in the leaf patterns of plants — most noticeable in the close-packed spirals of sunflower heads and fir cones.

Alan Turing was arrested and came to trial on 31 March 1952, after the police learned of his sexual relationship with a young Manchester man. He made no serious denial or defence, instead telling everyone that he saw nothing wrong with his actions. Rather than go to prison he accepted, for the period of a year, injections of oestrogen intended to neutralise his libido. Turing’s conviction led to the removal of his security clearance, and barred him from continuing with his cryptographic consultancy for GCHQ.

On 8 June 1954, Turing’s cleaner found him dead; he had died the previous day. When his body was discovered an apple lay half eaten beside his table. An inquest suggested that he had committed suicide, but his mother insisted that the ingestion was accidental. Biographer David Leavitt has suggested that Turing was re-enacting a scene from the 1937 film Snow White, his favourite fairy tale.

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