**Sierpiński**'s most important work is in the area of set theory, point set topology and number theory. In set theory he made important contributions to the axiom of choice and to the continuum hypothesis.

- This was a period of Russian occupation of Poland and it was a difficult time for the gifted Sierpiński to be educated in Poland.
- Despite the difficulties, Sierpiński entered the Department of Mathematics and Physics of the University of Warsaw in 1899.
- It is not surprising therefore that it would be the work of a Russian mathematician, one of his teachers Voronoy, that first attracted Sierpiński.
- Sierpiński was awarded the gold medal in the competition for his dissertation.
- Sierpiński was lucky for the lector changed the mark on his Russian language course to 'good' so that he could take his degree.
- The results in the prize essay that Sierpiński wrote in 1904 were a major contribution to a famous problem on lattice points.
- In 1913 Edmund Landau shortened Sierpiński's proof and described the result as profound.
- Let us digress for a moment to discuss some further work which flowed from this result of Sierpiński on what is often called the 'Gauss circle problem'.
- Sierpiński graduated in 1904 and worked for a while as a school teacher of mathematics and physics in a girls' school in Warsaw.
- However, when the school closed because of a strike, Sierpiński decided to go to Kraków to study for his doctorate.
- It was in 1907 that Sierpiński first became interested in set theory.
- Sierpiński began to study set theory and in 1909 he gave the first ever lecture course devoted entirely to set theory.
- Throughout his life Sierpiński maintained an incredible output of research papers and books.
- 1n 1912 he introduced the Sierpiński curve which describes a closed path which passes through every interior point of a square.
- About this time he introduced what is now called the Sierpiński triangle or Sierpiński gasket.
- Sierpiński was interned in Viatka.
- Sierpiński spent the rest of the war years in Moscow working with Luzin.
- In 1916, during his time in Moscow, Sierpiński gave the first example of an absolutely normal number, that is a number whose digits occur with equal frequency in whichever base it is written.
- Borel had proved such numbers exist but Sierpiński was the first to give an example.
- In 1920 Sierpiński, together with his former student Mazurkiewicz, founded the important mathematics journal Fundamenta Mathematicae.
- Sierpiński edited the journal which specialised in papers on set theory.
- From this period Sierpiński worked mostly in the area of set theory but also on point set topology and functions of a real variable.
- Sierpiński continued to collaborate with Luzin on investigations of analytic and projective sets.
- Sierpiński was also highly involved with the development of mathematics in Poland.
- Sierpiński continued working in the 'Underground Warsaw University' while his official job was a clerk in the council offices in Warsaw.
- Sierpiński was the author of the incredible number of 724 papers and 50 books.

Born 14 March 1882, Warsaw, Russian Empire (now Poland). Died 21 October 1969, Warsaw, Poland.

View full biography at MacTutor

Analysis, Origin Poland

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive