Editing Erdős number (section)

==Variations==
A number of variations on the concept have been proposed to apply to other fields, notably the [[Bacon number]] (as in the game [[Six Degrees of Kevin Bacon]]), connecting actors to the actor [[Kevin Bacon]] by a chain of joint appearances in films. It was created in 1994, 25 years after Goffman's article on the Erdős number.

A small number of people are connected to both Erdős and Bacon and thus have an [[Erdős–Bacon number]], which combines the two numbers by taking their sum. One example is the actress-mathematician [[Danica McKellar]], best known for playing Winnie Cooper on the TV series ''[[The Wonder Years]]''. 
Her Erdős number is 4,<ref>McKellar's co-author Lincoln Chayes published [https://projecteuclid.org/euclid.cmp/1103940982 a paper] with [[Elliott H. Lieb]], who in turn co-authored [https://doi.org/10.1016/0012-365X(71)90004-5 a paper] with [[Daniel Kleitman]], a co-author of Paul Erdős.</ref> and her Bacon number is 2.<ref>Danica McKellar was in ''[[The Year That Trembled]]'' (2002) with James Kisicki, who was in ''[[Telling Lies in America]]'' (1997) with Kevin Bacon.</ref>

Further extension is possible. For example, the "Erdős–Bacon–Sabbath number" is the sum of the Erdős–Bacon number and the collaborative distance to the band [[Black Sabbath]] in terms of singing in public. Physicist [[Stephen Hawking]] had an Erdős–Bacon–Sabbath number of 8,<ref>{{cite web|url=https://www.timeshighereducation.com/blog/whats-your-erdos-bacon-sabbath-number |title=What's your Erdős–Bacon–Sabbath number? |website=[[Times Higher Education]] |date=2016-02-17 |access-date=2018-07-29 |last=Fisher |first=Len}}</ref> and actress [[Natalie Portman]] has one of 11 (her Erdős number is 5).<ref>{{cite web|url=http://blogs.surrey.ac.uk/physics/2012/09/15/erdos-bacon-sabbath-numbers/comment-page-1/ |title=Erdős–Bacon–Sabbath numbers |date=2012-09-15 |access-date=2018-07-29 |last=Sear |first=Richard |website=Department of Physics, [[University of Surrey]]}}</ref>

In [[chess]], the [[Morphy number]] describes a player's connection to [[Paul Morphy]], widely considered the greatest chess player of his time and an unofficial [[World Chess Championship|World Chess Champion]].<ref>{{Cite web|last=Kingston|first=Taylor|title=Your Morphy Number Is Up|url=http://www.chesscafe.com/text/skittles258.pdf|url-status=live|archive-url=https://web.archive.org/web/20060613225534/http://www.chesscafe.com/text/skittles258.pdf|archive-date=13 June 2006|access-date=9 December 2020|website=Chesscafe}}</ref>

In [[go (game)|go]], the [[Honinbo Shusaku|Shusaku]] number describes a player's connection to Honinbo Shusaku, the strongest player of his time.<ref>{{Cite web|title=Shusaku Number|url=http://senseis.xmp.net/?ShusakuNumber|access-date=2023-04-07}}</ref><ref>{{Cite web|title=Shusaku Numbers|url=https://homepages.cwi.nl/~aeb/go/games/games/Shusaku/Shusaku-number/shusaku-number.html|access-date=2023-04-07}}</ref>

In [[video games]], the [[Ryu (Street Fighter)|Ryu]] number describes a video game character's connection to the [[Street Fighter]] character Ryu.<ref>{{cite news |title=Street Fighter's Ryu and Chun-Li join Ubisoft's take on Smash Bros., Brawlhalla |last=McWhertor |first=Michael |date=November 22, 2021 |publisher=Polygon |url=https://www.polygon.com/22796703/ubisoft-brawlhalla-street-fighter-ryu-chun-li-akuma |access-date=December 3, 2022}}</ref><ref>{{cite news |title=Street Fighter's Ryu Is The Kevin Bacon Of Video Games |last=Walker |first=Ian |date=June 22, 2021 |publisher=Kotaku |url=https://kotaku.com/street-fighter-s-ryu-is-the-kevin-bacon-of-video-games-1847150520 |access-date=December 3, 2022}}</ref>