“My brain is open!”
[Paul] Erdős (pronounced “air-dish”) structured his life to maximize the amount of time he had for mathematics. He had no wife or children, no job, no hobbies, not even a home, to tie him down. He lived out of a shabby suitcase and a drab orange plastic bag from Centrum Aruhaz (“Central Warehouse”), a large department store in Budapest. In a never-ending search for good mathematical problems and fresh mathematical talent, Erdős crisscrossed four continents at a frenzied pace, moving from one university or research center to the next. His modus operandi was to show up on the doorstep of a fellow mathematician, declare, “My brain is open,” work with his host for a day or two, until he was bored or his host was run down, and then move on to another home.
Erdős’s motto was not “Other cities, other maidens” but “Another roof, another proof.” He did mathematics in more than twenty-five different countries, completing important proofs in remote places and sometimes publishing them in equally obscure journals. Hence the limerick, composed by one of his colleagues:
A conjecture both deep and profound
Is whether the circle is round.
In a paper of Erdős
Written in Kurdish
A counterexample is found.
When Erdős heard the limerick, he wanted to publish a paper in Kurdish but couldn’t find a Kurdish math journal.