Pi Degrees of Separation
Numbers games and mathematics make a logical combination. So it’s no surprise that the maths world has its own version of the six degrees of separation game. Like the Hollywood game (created around actor Kevin Bacon) this one features a mathematician known for his prolific output: Paul Erdős.
Erdős was a Hungarian mathematician who published more than 1,500 research papers in his lifetime (1913—1996), more than anyone else in his field. He collaborated with other researchers on several hundred of these papers, and it is this high volume of collaborative works that provides the foundation for the six degrees game known as the Erdős Number.
A person’s Erdős Number is determined by whether they co-wrote a paper with him, or with someone else who collaborated with him. Paul Erdős has an Erdős Number of 0. His co-authors have an Erdős Number of 1. Anyone who has collaborated with one of his co-authors has an Erdős Number of 2, and so on.
Helpfully, an online calculator has been created to look up someone’s Erdős Number (or their degree of separation away from any other mathematician).
Spyros Heniadis has alerted me (in the comments below) to a great Radio Lab podcast which talks about the Erdős Number and Paul Erdős in more detail. It’s worth catching to hear about this extraordinary character, his unconventional life, upbringing and introduction to mathematics. The section on Erdős starts about halfway through the podcast.
Photo credit: Robbie Sproule