Alan Turing was an English scientist and mathematician. He was responsible for many important developments in the study of mathematics and computer science. He earned many distinctions throughout his career, and his work is considered pivotal to the development of the modern computer. Turing also devised an experiment known as the Turing test, which is still used by researchers to determine the authenticity of artificial intelligence.

## Early Life and Education

Alan Mathison Turing was born on June 23, 1912, in Paddington, London. His father, Julius Turing, traveled often for work, and Turing’s mother, Ethel, often joined her husband on his journeys. The couple wanted their children raised in London, so Turing and his older brother, John, were left to the care of family friends for many years. Turing showed a keen interest in the sciences from a very young age, and soon he was exhibiting a very high aptitude for subjects such as chemistry. His schoolteachers and headmasters took notice of Turing’s scientific talents while noting his poor English and writing skills.

Conventional schooling did not suit the freethinking Turing very well. He enjoyed finding new ways to solve problems in learning, particularly mathematics, and he often ignored the methods his teachers taught. By the time he finished school, he had earned multiple mathematics awards despite his unconventional style.

Turing became interested in the theory of relativity and eagerly studied the fields of physics, specifically quantum mechanics. He made a good friend in fellow schoolmate Christopher Morcom (1911–1930), who was also interested in scientific studies. He and Morcom worked together on their scientific ideas. Morcom became ill and died in 1930, however, an event that deeply affected the young Turing.

## College Years

Turing enrolled in King’s College in Cambridge in 1931 and studied mathematics. During his years at college, Turing delved deeper into many different scientific and mathematical disciplines. After graduating in 1934, he continued his education by taking advanced courses in mathematics. His studies in mathematical propositions and algorithms were of special interest to Turing, and he began working on his own ideas in the disciplines.

After submitting his thesis, “On the Gaussian Error Function,” which proved the central limit theorem of probability theory, Turing was named a fellow at King’s College in 1935. At this time, Turing became fascinated by the work of mathematician Kurt Gödel (1906–1978), specifically Gödel’s incompleteness theorems.

## The Turing Machine

In 1936, Turing reworked Gödel’s theories in his paper “On Computable Numbers, with an Application to the Entscheidungsproblem.” This paper introduced a hypothetical device known as an abstract machine, which later became known as a Turing machine. The device was designed to perform any mathematical computation presented in algorithmic form. Turing also hypothesized the creation of a “universal” Turing machine, which was capable of mechanically interpreting a variety of algorithms written out as standard sets of instructions. Turing imagined a single machine able to carry out all possible computational tasks. The Turing machine became highly influential in the computational theory discipline, and it eventually provided the basis for the concept of the modern computer. Turing’s studies in computation continued to influence the fields of mathematics and computer science for decades after its introduction.

Although Turing had created his theory independently, a Princeton University mathematician named Alonzo Church (1903–1995) had also come to a similar conclusion and had his work published first. This made it difficult for Turing to get his own work published, but this eventually was accomplished toward the end of 1936. That same year, Turing enrolled in graduate school at Princeton University, where he studied algebra and prime number theory. His time at Princeton culminated with the publication of his dissertation, *Systems of Logic Based on Ordinals*. Turing also spent his time at Princeton developing a cipher machine.

## Wartime Code Breaker

Turing returned to England in 1938, and World War II broke out the following year. He was recruited to work for the British cryptanalytic department at Bletchley Park where he and his colleagues were tasked with breaking the code on Germany’s Enigma cipher machine, which was used to relay messages to the German Navy. Throughout the early 1940s, Turing worked on developing a way to decode the Enigma messages. He eventually developed a machine called a Bombe, based on an existing Polish machine, which utilized a special statistical approach developed by Turing to decode German Navy signals. The Bombe was highly successful at decrypting German code, and Turing was awarded the Order of the British Empire in 1945 for his wartime contributions.

Following the war’s end, Turing was commissioned by London’s National Physical Laboratory to design a computer. He submitted a design for his Automatic Computing Engine (ACE), but the lab delayed building the computer. Turing eventually returned to Cambridge in 1947 to focus on other areas of interest, such as neurology and physiology. He continued to develop code for programming computers, however. Turing also became active in the athletic world, taking up marathon running and trying out for the 1948 British Olympic team. That same year, he resigned his post at the National Physical Laboratory to become a Reader at the University of Manchester. The model version of ACE was eventually built and executed its first program in 1950.

## Later Life

In 1950, Turing published *Computing Machinery and Intelligence*, a highly advanced work discussing the idea of artificial intelligence. The work introduced an experiment called the Turing test, which invented a standard that measured a machine’s ability to think. The test defined artificial intelligence as achieved if a person conversing with a machine could not tell it apart from a human. The Turing test is still the standard by which researchers measure artificial intelligence.

Turing was appointed a fellow of the Royal Society of London in 1951. He continued to delve into various mathematical theories and took an interest in applying them to biological systems. In 1952, he was arrested for violating British laws regarding same-sex acts, which were criminal offenses in England at the time. Turing reported himself to the police after being blackmailed over an affair with another man. He was tried and found guilty and ordered to receive hormone injections for one year, effectively making him impotent.

After his conviction, his security clearance at Bletchley Park was withdrawn because British law forbade security clearance to gay individuals. The British government kept a strict eye on Turing following his security clearance removal as it was worried he may divulge government secrets. Although he was open about his sexuality with his friends, Turing was not allowed to discuss his lifestyle in public due to British laws. On June 8, 1954, Turing was discovered dead by his housekeeper. The cause of death was cyanide poisoning, and the coroner ruled it a suicide.

## Legacy

Turing’s achievements were significant to the future of computer science. Alongside the Turing test and Turing machine, multiple scientific mechanisms have been named in his honor. A number of scholarly institutions have paid tribute to Turing by naming rooms, buildings, and awards after him. The Association for Computing Machinery (ACM) awards the Turing Award annually to individuals who make major contributions in the field of computers. The Turing Award is regarded as one of the most prestigious awards in computer science.

Turing’s life and career received further attention in the twenty-first century. In 2009, Prime Minister Gordon Brown (1951–) issued an apology on behalf of the British government for its treatment of Turing. In December 2013, Queen Elizabeth II (1926–) pardoned Turing, and the British government released a statement commending the scientist’s tremendous contributions. The following year, the film *The Imitation Game* was released in theaters. The docudrama chronicled Turing’s life from boyhood to adulthood and earned a number of prestigious film awards, further raising awareness of Turing’s life. The United Kingdom passed the Policing and Crime Act 2017, which includes the Alan Turing Law, pardoning all men convicted under the country’s since abolished same-sex relations laws.