Alan Turing
Turing c. 1928 at age 16
Alan Mathison Turing (1912 – 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing is widely considered to be the father of theoretical computer science and artificial intelligence. Turing was highly influential in the development of theoretical computer science, providing a formalisation of the concepts of algorithm and computation with the Turing machine, which can be considered a model of a general-purpose computer...which we now just call a computer.
Bletchley Park
During the Second World War, Turing worked for the Government Code and Cypher School at Bletchley Park, Britain's codebreaking centre that produced Ultra intelligence. For a time he led Hut 8, the section that was responsible for German naval cryptanalysis. Here, he devised a number of techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bombe method, an electromechanical machine that could find settings for the Enigma machine.
Bombe
Turing played a crucial role in cracking intercepted coded messages that enabled the Allies to defeat the Nazis in many crucial engagements, including the Battle of the Atlantic. Due to the problems of counterfactual history, it is hard to estimate the precise effect Ultra intelligence had on the war, but it has been estimated that this work shortened the war in Europe by more than two years and saved over 14 million lives.
The Automatic Computing Engine
After the war, Turing worked at the National Physical Laboratory, where he designed the Automatic Computing Engine. The Automatic Computing Engine was one of the first designs for a stored-program computer. In 1948, Turing joined Max Newman's Computing Machine Laboratory, at the Victoria University of Manchester, where he helped develop the Manchester computers and became interested in mathematical biology. He wrote a paper on the chemical basis of morphogenesis and predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, first observed in the 1960s. Turing was prosecuted in 1952 for homosexual acts; the Labouchere Amendment of 1885 had mandated that "gross indecency" was a criminal offence in the UK. He accepted chemical castration treatment, with DES, [to continue working] as an alternative to prison. Turing died in 1954, 16 days before his 42nd birthday, from cyanide poisoning.
Statue of Turing at Bletchley Park
Despite these accomplishments, he was never fully recognised in his home
country during his lifetime because much of his work was covered by the
Official Secrets Act. In 2009, following an Internet campaign, British
Prime Minister Gordon Brown made an official public apology on behalf of
the British government for "the appalling way he was treated". Queen
Elizabeth II granted Turing a posthumous pardon in 2013. The "Alan
Turing law" is now an informal term for a 2017 law in the United Kingdom
that retroactively pardoned men cautioned or convicted under historical
legislation that outlawed homosexual acts. Turing has an extensive
legacy with statues of him, many things named after him including an
annual award for computer science innovations. He is due to appear on
the Bank of England £50 note, to be released in June 2021.
A 2019 BBC series, as voted by the audience, named him the
greatest person of the 20th century.