Alan Mathison Turing, OBE, FRS (1912 - 1954)

Alan Turing was not a well known figure during his lifetime. But today he is famous for being an

eccentric yet passionate British mathematician, who conceived modern computing and played a crucial part in the Allied victory over Nazi Germany in WW2.

 

Turing spent much of his early life separated from his parents, as his father worked in the British

administration of India. At 13 years old, he was sent to Sherborne School, a large boarding school in

Dorset. The rigid education system gave his free ranging scientific mind little encouragement, so

Turing studied advanced modern scientific ideas, such as relativity, on his own, running far ahead of the

school syllabus.

 

"If he is to be solely a Scientific Specialist, he is wasting his

time at a Public School"

Alan Turing's Headmaster at Sherborne School

 

Photo: Science & Society Picture Library

Turing won a scholarship to King's College, Cambridge, and took the Mathematics degree with distinction. He thrived in a culture that encouraged his scientific interests and as a young gay man he also found protection in the liberal ambiance the college provided. At just 22, he was elected to a Fellowship. Turing was already on track for a distinguished career in pure mathematics. Yet his unusual interest in finding practical uses for abstract mathematical ideas was to push him in an altogether different direction.

 

Founder of modern computing

In 1936, Turing published a paper that is now recognised as the foundation of computer science. Turing analysed what it meant for a human to follow a definite method or procedure to perform a task. For this purpose, he invented the idea of a ‘Universal Machine’ that could decode and perform any set of instructions. Ten years later he would turn this revolutionary idea into a practical plan for an electronic computer, capable of running any program.

 

Breaking the Enigma code

In July 1939, the Polish Cipher Bureau passed on crucial information about the Enigma machine, which was used by the Germans to encipher all its military and naval signals. After September 1939, joined by other mathematicians at Bletchley Park, Turing rapidly developed a new machine (the ‘Bombe’) capable of breaking Enigma messages on an industrial scale. In 1941, Turing’s section, ‘Hut 8’, mastered the German submarine communication system that was vital to the battle of the Atlantic.

 

The Germans were convinced that Enigma output could not be broken,

so they used the machine for all sorts of communications on the

battlefield, at sea, in the sky and, significantly, within its secret services.

The British described any intelligence gained from Enigma as 'Ultra',

and considered it top secret. Only a select few commanders were

made aware of the full significance of Ultra, and used it sparingly to

prevent the Germans realising their ciphers had been broken.

 

After the war

In March 1946 Turing produced a detailed design for what was called

the Automatic Computing Engine (ACE.) This was a digital computer

in the modern sense, storing programs in its memory. His report

emphasised the unlimited range of applications opened up by this

technological revolution, and software developments ahead of parallel

American developments. Yet his relationship with NPL soured and he l

eft in 1948, before a pilot version of the ACE was made in 1950.

 

Turing moved to the University of Manchester, where electronic engineers had already demonstrated a very small stored-program computer. Now he focused on the use of computers. His main theme had been in investigating the power of a computer to rival human thought. In 1950, he published a philosophical paper including the idea of an ‘imitation game’ for comparing human and machine outputs, now called the Turing Test. This paper remains his best known work and was a key contribution to the field of Artificial Intelligence.

 

In 1951 Turing turned to a completely new scientific project, which exploited his ability to use the Manchester computer. It was the problem of understanding the biological patterns – spots, stripes, flower petals – of nature. He proposed an explanation in terms of chemical interactions and developed equations for them. His paper on this theory, completed in 1951, became a classic and is still the subject of intense investigation 60 years later. In the same year he was elected a Fellow of the Royal Society for his earlier work.

 

Final years

Turing was also a victim of mid 20th Century attitudes to homosexuality. All male homosexual activity was illegal until 1967, and in 1952 Turing was prosecuted when an affair with a young man came to the notice of the police. His security clearance was revoked, ending ongoing work with the government code-breaking department. Following this he was harassed by police surveillance.

Alan Turing committed suicide in 1954.

 

In December 2013, Alan Turing was granted a posthumous royal pardon, formally cancelling his criminal conviction. It followed a four-year campaign supported by tens of thousands of people, including scientists Stephen Hawking and Richard Dawkins. Opinion was divided on whether singling out an individual in this way did true justice to a situation in which thousands of gay men had been criminalised.

 

Photo: Science & Society Picture Library • Also in Public Domain