Paul Erdős lived out of a suitcase and co-wrote with 500 mathematicians
For most of his adult life Paul Erdős had no fixed home. He travelled from one colleague to the next, expecting hosts to feed him, house him and wash his clothes, and in return produced around 1,500 papers with more than 500 co-authors, a record that inspired the Erdős number.
Born in Budapest in 1913, a few days after both his young sisters died of scarlet fever, he was the only surviving child of two mathematics teachers. His father spent 1914 to 1920 as a prisoner of war in Siberia, taught himself English there with odd pronunciation, and passed that accent to his son for life. At five the boy could work out in his head how many seconds someone had lived.
He entered the University of Budapest at 17 despite quotas restricting Jewish students, and by 21 had his doctorate under Lipót Fejér, who also supervised John von Neumann. A student circle meeting by the Anonymous statue in City Park produced a geometry puzzle from Esther Klein; Erdős and George Szekeres generalised it in 1935, and he named it the Happy Ending problem because Klein and Szekeres married.
Hungary became dangerous for Jews, and he left for Princeton in 1938. Wandering suited him. In 1941 he was arrested near a secret radio tower, reportedly explaining he had been thinking about theorems rather than reading the warning signs, and the FBI kept a file on him into the 1970s without finding anything. In 1954 the United States refused him re-entry amid McCarthyism, partly over letters to a Chinese mathematician, so he spent about a decade based in Israel until a visa came through in November 1963. Communist Hungary, meanwhile, granted him the rare freedom to come and go as he pleased.
He loved working with children, meeting a 10-year-old Terence Tao in Adelaide in 1985. His specialities were discrete mathematics, graph theory and Ramsey theory, and he kept at it until the end, dying at a mathematics conference in Warsaw in 1996.
Source: Paul Erdős
