Alan Turing

In 1936, at just 24 years old, Alan Turing published his landmark paper, 'On Computable Numbers, with an Application to the Entscheidungsproblem'. In it, he resolved David Hilbert's fundamental question of whether mathematics could be fully mechanized by proving that no universal algorithm exists to determine whether an arbitrary mathematical statement is provable.

To prove this, Turing introduced the concept of an abstract computing device—now called the Turing Machine—consisting of an infinite tape, a read/write head, and a state register. He demonstrated that a single 'Universal Turing Machine' could simulate the operation of any other computing machine by reading its program from the tape, inventing the conceptual foundation of the stored-program computer.

During World War II, Turing was a leading codebreaker at the Government Code and Cypher School (GC&CS) at Bletchley Park. He headed Hut 8, the section responsible for decrypting German naval Enigma messages.

Turing designed the electromechanical 'Bombe' machine, which could test thousands of potential Enigma rotor configurations simultaneously. His statistical method of 'Banburismus' drastically reduced the number of tests required, allowing allied naval forces to intercept and avoid U-boat wolfpacks in the Battle of the Atlantic, shortening the war in Europe by an estimated two to four years.

In 1950, Turing published his seminal philosophical paper 'Computing Machinery and Intelligence' in the journal Mind. He opened with the question, 'Can machines think?' and proposed what is now known as the Turing Test (the Imitation Game): if a human evaluator cannot reliably distinguish between text conversations with a machine and a human, the machine exhibits intelligent behavior.