The Erdős-Bacon number is a way to measure how connected an actor or actress is to the famous mathematician Paul Erdős. To get an Erdős number, you need to have collaborated on a research paper with someone who has collaborated with Erdős. Actors and actresses can get a Bacon number by appearing in a movie with Kevin Bacon or appearing in a movie with someone who appears in a movie with Kevin Bacon.
If someone has an Erdős number of 2 and a Bacon number of 2, they have an Erdős-Bacon number of 4 (2 + 2 = 4). This means they are only four connections away from both the famous mathematician and actor Kevin Bacon.
The Erdős-Bacon number became a popular topic in recent years, as people began to search for celebrities with low Erdős-Bacon numbers. Many notable people have surprisingly low numbers, meaning they are connected to both Bacon and Erdős in just a few steps.