# Waclaw Sierpinski

**Waclaw Franciszek Sierpiński**, was born on March 14, 1882 in Warsaw and died on October 21, 1969 in Warsaw. He was a Polish mathematician, known for outstanding contributions to set theory (research on the axiom of choice and the continuum hypothesis), number theory, theory of functions and topology. He published over 700 papers and 50 books (two of which, "Introduction to General Topology" (1934) and "General Topology" (1952) were later translated into English by the Canadian mathematician Cecilia Krieger).

Two well-known fractals are named after him (the Sierpinski triangle and the Sierpinski carpet), as are Sierpinski numbers and the associated Sierpinski problem.

Sierpinski enrolled in the Department of Mathematics and Physics at the University of Warsaw in 1899 and graduated four years later. In 1903, while still at the University of Warsaw, the Department of Mathematics and Physics offered a prize for the best essay from a student on Voronoy's contribution to number theory. Sierpinksi was awarded a gold medal for his essay, thus laying the foundation for his first major mathematical contribution. Unwilling for his work to be published in Russian, he withheld it until 1907, when it was published in Samuel Dickstein's mathematical magazine 'The Works of Mathematics and Physics'.

After his 1904 graduation, Sierpinski worked for as a school teacher of mathematics and physics in Warsaw. However when the school closed because of a strike, Sierpinski decided to go to Krakóv to pursue doctorate. At the Jagiellonian University in Krakóv he attended lectures by Zaremba on mathematics. He also studyied astronomy and philosophy. He received his doctorate and was appointed to the University of Lvov in 1908.

In 1907 that Sierpinski first became interested in set theory when he came across a theorem which stated that points in the plane could be specified with a single coordinate. He wrote to Banachiewicz (then at Göttingen), asking him how such a result was possible. He received a one word reply 'Cantor'. Sierpinski began to study set theory and, in 1909, he gave the first ever lecture course devoted entirely to the subject.

Sierpinski maintained an incredible output of research papers and books. During the years 1908 to 1914, when he taught at the University of Lvov, he published three books in addition to many research papers. These books were The Theory of Irrational Numbers (1910), Outline of Set Theory (1912), and The Theory of Numbers (1912).

When World War I began in 1914, Sierpinski and his family were in Russia. To avoid the persecution that was all to common for Polish foreigners, Sierpinski spent the rest of the war years in Moscow working with Luzin. Together they began the study of analytic sets. In 1916, Sierpinski gave the first example of an absolutely normal number.

When World War I ended in 1918, Sierpinski returned to Lvov. However shortly after taking up his appointment again in Lvov he was offered a post at the University of Warsaw, which he accepted. In 1919 he was promoted to professor at Warsaw and he spent the rest of his life there.

In 1920 Sierpinski, together with his former student Mazurkiewicz, founded the important mathematics journal Fundamenta Mathematica. Sierpinski edited the journal, which specialized in papers on set theory.

During this period, Sierpinski worked predominately on set theory, but also on point set topology and functions of a real variable. In set theory he made contributions on the axiom of choice and on the continuum hypothesis. He also worked on what is now known as the Sierpinski curve. Sierpinski continued to collaborate with Luzin on investigations of analytic and projective sets. His work on functions of a real variable include results on functional series, differentiability of functions and Baire's classification.

Sierpinski was also highly involved with the development of mathematics in Poland. He was honoured with election to the Polish Academy in 1921 and was made dean of the faculty at the University of Warsaw the same year. In 1928 he became vice-chairman of the Warsaw Scientific Society and, in the same year, was elected chairman of the Polish Mathematical Society.

Sierpinski authored 724 papers and 50 books. He retired in 1960 as professor at the University of Warsaw, but he continued to give a seminar on the Theory of Numbers at the Polish Academy of Sciences up to 1967. He also continued his editorial work, as editor-in-chief of Acta Arithmetica, and as an editorial board member of Rendiconti dei Circolo Matimatico di Palermo, Composito Matematica and Zentralblatt für Mathematik.

Honorary Degrees: Lvov (1929), St. Marks of Lima (1930), Amsterdam (1931), Tarta (1931), Sofia (1939), Prague (1947), Wroclaw (1947), Lucknow (1949), and Lomonosov of Moscow (1967).

He was elected to the Geographic Society of Lima (1931), the Royal Scientific Society of Ličge (1934), the Bulgarian Academy of Sciences (1936), the National Academy of Lima (1939), the Royal Society of Sciences of Naples (1939), the Accademia dei Lincei of Rome (1947), the German Academy of Science (1950), the American Academy of Sciences (1959), the Paris Academy (1960), the Royal Dutch Academy (1961), the Academy of Science of Brussels (1961), the London Mathematical Society (1964), the Romanian Academy (1965) and the Papal Academy of Sciences (1967).

Sierpinski was awarded the scientific prize of the first degree in 1949.

Waclaw Sierpinski is interred in the Powazki Cemetery, Warsaw, Poland.