Alan Turing: the Man Behind the Enigma

This blog post was written by ScienceGrrl Glasgow’s own Shona Ferguson.

The very laptop with which I write this blog post and, very probably, whatever device you happen to be reading it on both use technology first conceptualized by a man named Alan Turing. Imagine, hypothetically, that you have been transported to the 1940s. Would you be able to explain the concept of a computer? Could you describe its inner workings? Turing created the ideas behind algorithms and computer programs in a time when ‘computers’ were people who performed mathematical calculations. During his lifetime, much of his efforts went unrecognized due to his homosexuality and the fact that a large portion of his work was covered by the Official Secrets Act. In honour of Pride month, let’s shed some light on Alan Turing’s life and accomplishments.

Early Years

Alan Turing in 1928, age 16. By Unknown author – http://www.turingarchive.org/viewer/?id=521&title=4, Public Domain, https://commons.wikimedia.org/w/index.php?curid=22828488

We might as well start at the beginning. Born in London on the 23^rd of June 1912, Alan Mathison Turing was an exceptional mathematician known for his ground-breaking contributions to fields such as cryptanalysis, computer science, philosophy and theoretical biology. He was the youngest child of Julius Mathison Turing, a British member of the Indian Civil Service, and Ethel Sara Stoney, daughter of the chief engineer of the Madras railways. As children, both Alan and his brother John were fostered in several English homes as their parents lived in India until their father’s retirement in 1926. This was also the year in which Turing was accepted into Sherborne School and was the year of the general strike which caused him to have to cycle 60 miles to the school as he was unable to get the train. His ease at this task was perhaps an indication of the almost Olympic level athlete he was to become. At school, he struggled to follow the conventional methods taught to him, often following his own train of original thought. Turing’s headmaster reported, “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 Public School.”

There was at least one positive to come of Turing’s school years. In 1928, he formed a close friendship with Christopher Morcom who was in the year above. The two shared a period of intellectual companionship and were able to share their scientific thoughts and ideas. Unfortunately, their time together was short-lived due to Morcom’s sudden death in February of 1930. Subsequent to his friend’s death, Turing became interested in the subject of the human mind and its association with matter.

University Years

In contrast to his experience at school, Turing was free to explore his own thoughts and ideas during his time at King’s College, Cambridge as a mathematics undergraduate. He began his studies in 1931 and started to show interest in mathematical logic two years later. For those of you who don’t know, mathematical logic is a subfield of maths involving the applications of formal logic to maths. It encompasses set theory, model theory, recursion theory, and proof theory. I could define each of those as well but I can almost hear you begging me not to so I shall refrain before we get stuck down the definition rabbit hole that is mathematics!

You may remember from history classes that Hitler’s rise in Germany and Britain’s anti-war movement both occurred in 1933. Turing was part of the anti-war movement but did not drift towards Marxism, nor pacifism. He completed his undergraduate degree in 1934 and went on to be elected a fellow of King’s College a year later for his work on probability. This work also won him a Smith’s Prize in 1936.

We return now to the topic of mathematical logic. Turing attended a lecture course by Cambridge topologist Max Newman in 1935 where he learnt of Hilbert’s then unanswered question on decidability, known as the Entsheidungsproblem. As simply as possible, decidability is the concept of whether there exists a method by which you could decide whether any given mathematical proposition is provable (if you’re like me, you may have to read that a few times!). Turing proceeded to consider this question in greater depth.

The Turing Machine

After attending Newman’s course, Turing published On Computable Numbers, with an application to the Entsheidungsproblem. This 1936 paper proposed the idea of an abstract machine with the ability to perform elementary operations using symbols on paper tape. This is now known as a “Turing machine” but can also be thought of as a computer program. In the same paper, Turing also defined a ‘definite method’ – now known as an algorithm – which was used to prove that the method described in Hilbert’s decidability question does not exist.

The publication of Turing’s paper was unfortunately delayed due to the work of American mathematician Alonzo Church who published An unsolvable problem in elementary number theory in 1936 which drew the parallel conclusion that there is no decision procedure for arithmetic. The case for publication of Turing’s paper by the London Mathematical Society was argued on the basis of Turing’s original, and altogether different, approach to the subject at hand. A revised version of his paper which referenced Church made it to print in 1937. In the present day, the Turing machine is seen as the foundation of modern computer science.

In addition to the Turing machine, Turing also introduced the notion of a Universal Turing machine. He claimed that such a machine would carry out any computation depending on the instructions of the tape inserted into it. As stated previously, a ‘computer’ during this time period would have been defined as a person who performed a computation. Nevertheless, it is clear to see that what Turing described as the Universal Turing machine would be what we think of as a computer today. All this imaginative mathematics existed only in Turing’s mind in 1936 and, in fact, the technology to physicalize his ideas at a practical level did not come to be until 9 years later.

As a result of discussions between Church and Turing on their similar work, Turing became a graduate student at Princeton University in 1936 where he worked on algebra and number theory and produced a PhD thesis on Ordinal Logics. Soon after his return to England in 1938, Turing began to work on breaking the German Enigma codes for the Government Code and Cipher School in preparation for the looming war with Germany.

The Second World War and Bletchley Park

Immediately after the declaration of war in 1939, Turing moved to Bletchley Park to work full-time at the Government Code and Cipher School. The work taking place at Bletchley Park was covered by the Official Secrets Act and went largely unrecognized until the mid-70s when the work started to become public knowledge. Turing thrived at Bletchley Park as he was able to fully embrace his inventiveness and he got on with his fellow workers.

Turing collaborated with fellow mathematician W G Welchman to develop a machine called the Bombe with help from information gifted by Polish mathematicians in July 1939. From late 1940 onwards, the Bombe decoded all messages of the Luftwaffe. However, decoding the messages sent via the Enigma machines of the German navy was a more challenging task for Turing. It was not until mid-1941 that German navy signals were able to be decoded thanks to the capture of more information and some complex statistical methods.

Despite these great efforts, the German Enigma machines were given an extra complication in 1942 meaning Bletchley Park were completely unable to decode the new messages. From November 1942 until March 1943, Turing was in the United States helping with decoding issues and a speech secrecy system. Although he was not present for the decryption of the more complex codes, Turing’s ideas were of great value in this work. He was awarded an OBE in 1945 for his vital contribution to the war effort.

Replica of the *Bombe* now at the National Museum of Computing on Bletchley Park.

Computer Designer

After the war, Turing was invited to the National Physical Laboratory in London to design an electronic computer. In 1946, he submitted a report proposing his design for the Automated Computing Engine (ACE) which was an electronic stored-program all-purpose digital computer. At the time, Turing’s design was viewed as over-ambitious due to its high speed and large storage space, and so the project experienced several delays.

Perhaps out of frustration at the lack of cooperation during his work for NPL, Turing returned to Cambridge for the academic year 1947-48 to study very different topics, namely neurology and physiology. There was no advance in construction of the ACE at NPL during this time and thus the world’s first working electronic stored-program digital computer was built instead by the Royal Society Computer Machine Laboratory at the University of Manchester.

In another unexpected twist, Turing had begun to run in amateur athletic competitions after the war and was very skilled at cross-country and long-distance running. If not for injury, he may have had a strong chance of competing in the 1948 Olympic Games.

Last Years

In 1948, Turing was offered a post at the computing laboratory of the University of Manchester and, in order to accept the offer, he resigned from the National Physical Laboratory. Two years later, Turing published Computing machinery and intelligence in the philosophical journal Mind. In this paper he proposed the Turing Test to determine whether a computer is capable of ‘thinking’ like a human being. It also gave rise to some of the core problems of artificial intelligence and is today considered a classic contribution to the field.

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

For his earlier mentioned work on Turing machines, Turing was elected a Fellow of the Royal Society of London in 1951. At this time he was working on the application of mathematical theory to biological forms and submitted the paper The Chemical Basis of Morphogenesis that November.

In 1952, Alan Turing was arrested for violation of British homosexuality statutes after the police learned of his sexual relationship with another man. Turing was always open about his sexuality and so did nothing to deny the charges, instead stating that he had done nothing wrong. After being found guilty, he was offered a prison sentence or a year of oestrogen injections to neutralise his libido and chose the latter.

Despite the horrific treatment he had received, Turing then returned to his many academic pursuits. He worked on topics such as morphogenesis, quantum theory, and relativity theory. Turing also secretly returned to decoding and intelligence work at GCHQ although his security clearance was removed after his conviction.

Sadly, on June 7^th 1954, Alan Turing died of cyanide poisoning at the age of 41. Cyanide was found on a half-eaten apple beside his bed and the coroner concluded that his death was suicide. However, his mother maintained that his death was simply an accident caused by an experiment gone wrong.

Turing was posthumously granted a royal pardon by Queen Elizabeth II in December of 2013 and, three years later, the British government introduced “Turing’s Law” which serves to pardon men who were convicted of homosexual acts before they were legalised. These were important steps in the road to equality which may never have come to be without the remarkable accomplishments of Alan Mathison Turing