Paul Erdős Lived in a Suitcase

Paul Erdős was born in Hungary in 1913 and died in Warsaw in 1996 at a mathematics conference. In between, he published roughly 1,500 papers with about 512 co-authors, more than any mathematician before or since. He did this while owning almost nothing. He traveled with two suitcases, subsisted on speaking fees and a small stipend, and lived in the homes of fellow mathematicians, sometimes for weeks, bouncing from Budapest to Princeton to Los Angeles to Tel Aviv.

His method was collaborative saturation. He would arrive at a colleague's home, drink what he called "Benzedrine coffee" — amphetamines, which he used openly for decades — and work from roughly breakfast until the host collapsed. He'd move to the next mathematician in his network. Ronald Graham, who handled Erdős's finances and correspondence for decades, kept a room at Bell Labs he referred to as the "Erdős room." Erdős called children "epsilons," women "bosses," and God "the Supreme Fascist."

The Erdős number is the social graph he left behind. Your Erdős number is the minimum number of co-authorship steps between you and him. Einstein's is 2. Most working mathematicians have finite Erdős numbers, as do many physicists and computer scientists. Natalie Portman has an Erdős number of 5, via her undergraduate thesis advisor. It has been computed for about 10,000 Nobel laureates in physics.

He had almost no money of his own, but he gave away prizes — small sums, "Erdős problems," offered for proofs of conjectures he cared about. He paid for a $10,000 prize on the Collatz conjecture out of pocket. When he died, his friends said the correct formulation of his life was that he'd been a node — not a person who knew a lot of mathematicians, but a structural element in the mathematical community that let other nodes find each other.