Felix Hausdorff
Born: 8 Nov 1868 in Breslau, Germany (now Wroclaw,
Poland)
Died: 26 Jan 1942 in Bonn,
Germany
Felix Hausdorff graduated from Leipzig in 1891 and then taught there until 1910 when he went to Bonn. Within a year of his appointment to Leipzig he was offered a post at Göttingen but, rather surprisingly given Göttingen's reputation, he turned it down. Hausdorff worked at Bonn until 1935 when he was forced to retire by the Nazi regime. Although as early as 1932 he sensed the oncoming calamity of Nazism he made no attempt to emigrate while it was still possible.
As a Jew his position became more and more difficult. In 1941 he was scheduled to go to an internment camp but managed to avoid being sent. However by 1942 he could no longer avoid being sent to the internment camp and, together with his wife and his wife's sister, he committed suicide.
Hausdorff's main work was in topology and set theory. He
introduced the concept of a partially ordered set and from 1906 to 1909 he
proved a series of results on ordered sets. In 1907 he introduced special types
of ordinals in an attempt to prove Cantor's
continuum hypothesis. He
also posed a generalisation of the continuum hypothesis by asking if 2 to the
power 
n was
equal to n+1. Hausdorff proved
further results on the cardinality of Borel
sets in 1916.
Building on work by Fréchet and others, he created a theory of topological and metric spaces with Grundzüge der Mengenlehre (1914). Earlier results on topology fitted naturally into the framework set up by Hausdorff.
In 1919 he introduced the notion of Hausdorff dimension, which
was a real number lying between the topological dimension of an object and 3. It
is used to study objects such as Koch's
curve. He also introduced the Hausdorff measure and the term 'metric space' is
due to him.