In 1936, Alan Mathison
Turing published an alternative to
universal coding language of 1931,
by introducing what's now known as the
Turing machine (TM) .
In 1935, Turing's advisor Alonzo Church
had already extended Gödel's results on the limits
of proof and computation, by solving the famous Entscheidungsproblem,
using his own alternative universal language called Lambda calculus, basis of LISP.
In the following year,
Turing used his TMs
to do the same . TMs
subsequently became a widely used abstract model of
During World War II Turing helped (with Gordon Welchman)
to decipher the Nazi code,
using the Colossus machine designed by Tommy Flowers,
building on earlier work by Polish mathematicians
Marian Rejewski, Jerzy Rozycki and Henryk Zygalski
who first broke the Enigma code.
Some sources say this work was decisive
for defeating the Third Reich.
Later Turing suggested his famous test for evaluating
whether a computer is intelligent (more on Artificial Intelligence history).
Computer science's most sought after prize carries his name:
the Turing award.
1912: Born in London.
1931: King's College, Cambridge.
1936: most famous paper at age 30 .
1939-1942: Bletchley Park, helping to decode the Luftwaffe's Enigma code.
1950: Turing test.
1954: Suicide in Wilmslow.
. A. M. Turing.
On computable numbers, with an application to the
Entscheidungsproblem. Proceedings of the London
Mathematical Society, Series 2, 41:230-267, 1936.
The letter below appeared in
Nature 429, 501 (03 June 2004);
doi:10.1038/429501c; © Macmillan Publishers Ltd.
Turing's war work counts for more than computers
Sir - John L. Casti, in his fine review of Alan Turing: Life and Legacy of
a Great Thinker, edited by Christof Teuscher ("Touring artificial minds"
Nature 428, 258; 2004), proposes that Turing had more impact on everyday
life than the man named by Time magazine as Person of the Century,
(Time 154, 27; 1999). Casti suggests that Turing's 1936
paper provided the "theoretical backbone" for all computers to come.
Although Turing, a hero of mine, certainly was one of the greatest,
we should keep in mind that his paper essentially just elegantly
1931 results and Alonzo Church's extension
thereof. It did not have any impact on the construction of the first
working program-controlled computer. That was made in Berlin by
in 1935-1941 and was driven by practical considerations, not
In fact, the greatest impact that Alan Turing made on daily life was
probably through his contribution to cracking the Enigma code, used
by the German military during the Second World War, which is sometimes
cited as a decisive event of the war.
Dalle Molle Institute for Artificial
Intelligence (IDSIA), Switzerland
But who was really the most influential person of the
20th century? It was none of those mentioned in the
letter to the left: neither
And it was neither Hitler nor Gandhi, for that matter.
At least scientists know that the most influential TwenCen persons
Fritz Haber & Carl Bosch.
Never heard of them?
They were the ones whose invention jump-started the population
explosion - billions of people would not even exist without the