# Erdős–Bacon number

A person's Erdős–Bacon number is the sum of their Erdős number—which measures the "collaborative distance" in authoring academic papers between that person and Hungarian mathematician Paul Erdős—and their Bacon number—which represents the number of links, through roles in films, by which the person is separated from American actor Kevin Bacon. The lower the number, the closer a person is to Erdős and Bacon, which reflects a small world phenomenon in academia and entertainment.
To have a defined Erdős–Bacon number, it is necessary to have both appeared in a film and co-authored an academic paper, although this in and of itself is not sufficient as one's co-authors must have a known chain leading to Paul Erdős, and one's film must have actors eventually leading to Kevin Bacon.

## Academic scientists
### 4

Physicist Nicholas Metropolis has an Erdős number of 2, and also a Bacon number of 2 via the Woody Allen film Husbands and Wives, giving him an Erdős–Bacon number of 4.

### 6

Metropolis and Richard Feynman both worked on the Manhattan Project at Los Alamos Laboratory. Via Metropolis, Feynman has an Erdős number of 3 and, from having appeared in the film Anti-Clock alongside Tony Tang, Feynman also has a Bacon number of 3. Richard Feynman thus has an Erdős–Bacon number of 6.
Theoretical physicist Stephen Hawking has an Erdős–Bacon number of 6: his Bacon number of 2 (via his appearance alongside John Cleese in Monty Python Live (Mostly), who acted alongside Kevin Bacon in The Big Picture) is lower than his Erdős number of 4.
Linguist Noam Chomsky has an Erdős number of 4, he also co-starred with Danny Glover in the 2005 documentary The Peace!, giving him a Bacon number of 2 and combined Erdős–Bacon number of 6.

### 7

Scientist Carl Sagan has an Erdős–Bacon number of 6, from a Bacon number of 3 and an Erdős number of 4.

## Actors
### 4

Canadian actor Albert M. Chan has Erdős–Bacon number of 4. He co-authored a peer-reviewed paper on orthogonal frequency-division multiplexing, giving him an Erdős number of 3. Chan appeared alongside Kevin Bacon in Patriots Day, giving him a Bacon number of 1.

### 6

American actress Danica McKellar, who played Winnie Cooper in The Wonder Years, has an Erdős–Bacon number of 6. While an undergraduate at the University of California, Los Angeles, McKellar coauthored a mathematics paper with Lincoln Chayes, who via his wife Jennifer Tour Chayes has an Erdős number of 3, giving McKellar one of 4. Having worked with Margaret Easley, McKellar has a Bacon number of 2.
British actor Colin Firth has an Erdős–Bacon number of 6. Firth is credited as co-author of a neuroscience paper, "Political Orientations Are Correlated with Brain Structure in Young Adults", after he suggested on BBC Radio 4 that such a study could be done. Another author of that paper, Geraint Rees, has an Erdős number of 4, which gives Firth an Erdős number of 5. Firth's Bacon number of 1 is due to his appearance in Where the Truth Lies.

### 7

Israeli-American actress Natalie Portman has an Erdős–Bacon number of 7. She collaborated (using her birth name, Natalie Hershlag) with Abigail A. Baird, who has a collaboration path leading to Joseph Gillis, who has an Erdős number of 1, giving Portman an Erdős number of 5. Portman appeared in A Powerful Noise Live (2009) with Sarah Michelle Gellar, who appeared in The Air I Breathe (2007) with Bacon, giving Portman a Bacon number of 2.
American actress Kristen Stewart has an Erdős–Bacon number of 7; she is credited as a co-author on an artificial intelligence paper that was written after a technique was used for her short film Come Swim, giving her an Erdős number of 5, and she co-starred with Michael Sheen in Twilight, who co-starred with Bacon in Frost/Nixon, giving her a Bacon number of 2.

## Others

Sergey Brin has an Erdős number of 3 through papers with Jeffrey Ullman and Ronald Graham, and he has two cameos in the 2013 comedy The Internship, leading to a Bacon number of 2 via Rose Byrne and consequently an Erdős–Bacon number of 5.
Bill Gates has an Erdős number of 4 and in 1987 he participated in a short mockumentary titled Citizen Steve about Steven Spielberg, where he co-starred with Whoopi Goldberg, giving him a Bacon number of 2 and consequently an Erdős–Bacon number of 6.

## Table

| Name | Erdős number | Bacon number | Erdős–Bacon number |
| Mayim Bialik | 5 | 2 | 7 |
| Brian Cox | 7 | 3 | 10 |
| Richard Feynman | 3 | 3 | 6 |
| Colin Firth | 5 | 1 | 6 |
| Stephen Hawking | 4 | 2 | 6 |
| Daniel Kleitman | 1 | 2 | 3 |
| Danica McKellar | 4 | 2 | 6 |
| Nicholas Metropolis | 2 | 2 | 4 |
| Natalie Portman | 5 | 2 | 7 |
| Carl Sagan | 4 | 2 | 6 |
| Kristen Stewart | 5 | 2 | 7 |
Notes:
* 1 2 3 Includes role as self.
* 1 2 3 See discussion above (Actors).