-> ''I know a guy, who knows a guy,''
-> ''who knows a guy, who knows a guy,''
-> ''who knows a guy, who knows... Kevin Bacon!''
-->-- Music/WeirdAlYankovic, "[[Music/MandatoryFun Lame Claim to Fame]]"[[note]]"Weird Al" Yankovic himself has a Bacon number of 2, he was in ''Film/SpyHard'' with Creator/AndyGriffith who was in the made-for-tv film ''The Demon Murder Case'' with Kevin Bacon.[[/note]]

This is a pop-culture game, whose title is a {{mondegreen}} of ''Theatre/SixDegreesOfSeparation'', in which it is said that anyone in the entertainment business can be linked through their film roles to the actor Creator/KevinBacon within six steps.

In other words, pick a random actor. '''Any''' actor. Now think of someone they've ever been in a movie with. Now think of a chain of such individuals, each of whom has been in a film with a ''different'' person, until you reach somebody who's been in one with Kevin Bacon -- and thereby link to the man himself, in as few steps as possible. For example: Creator/GeorgeClooney was in ''Film/OceansEleven'' with Creator/MattDamon, Matt Damon was in ''Film/TheDeparted'' with Creator/JackNicholson, and Jack Nicholson was in ''Film/AFewGoodMen'' with... Kevin Bacon. ''Voilà.''

Mathematicians have extrapolated this phenomenon and given it a name: "Bacon Number", which sounds like one of those impossibly high numbers with dangerous implications for the future of the Universe but is in fact incredibly low. In the example above, Clooney has a Bacon Number of 3: three degrees of separation from the target individual. Damon has a Bacon Number of 2, and Nicholson has the lowest attainable Bacon Number of 1. Kevin Bacon, himself, has the unique Bacon Number of 0.

Every actor has a Bacon Number, even voice actors.[[note]](For example, Kevin Bacon voiced the title character in ''WesternAnimation/{{Balto}}''.)[[/note]] Most players agree that the game should be limited to feature-length films; some vary on whether or not to include animation or documentaries.

And it's not just actors, per se. As implied in the first paragraph above, you can play it with literally ''anybody'' who's ever appeared in a film. Try, oh, Creator/AndyWarhol. He made an uncredited cameo in ''Film/{{Tootsie}}'', starring Creator/DustinHoffman, who was in ''Film/{{Sleepers}}'' with Kevin Bacon -- giving Warhol a Bacon Number of 2. Creator/DavidLetterman? Same. He was in ''Film/ManOnTheMoon'', as was Creator/DavidKoechner who acted alongside Bacon in ''My One And Only''. Or how about a man who was ''literally'' on the moon? UsefulNotes/BuzzAldrin appeared in ''Film/TransformersDarkOfTheMoon'', as did Creator/JohnMalkovich, who was in ''Film/QueensLogic'' with KB. That's a Bacon Number of 2 for Aldrin too. And so on.

There is a whole website, The Oracle of Bacon, dedicated to this that is [[http://oracleofbacon.org/index.php found here.]] The site's algorithms originally used the Website/{{IMDb}} for tracing its web of connections, before moving to Website/{{Wikipedia}} and finally The Movie Database ([[https://www.themoviedb.org/ TMDB]]).

For applications in fiction, see OneDegreeOfSeparation.
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!! Center of the Hollywood Universe
Whisper it, but there isn't really anything special (in this context) about Kevin Bacon -- bar his name's happy resemblance to the word "separation".

Anybody who's been in Hollywood for any length of time will, the chances are, represent their own Ground Zero in a comparable network of radiating interconnections. There are a few key factors: appearing in large casts, and/or with people who themselves have acted alongside a whole lot of other people, are quick ways of establishing a significant number of close connections. Long-term, featuring in a diverse range of productions will broaden the web of possible links.

Certainly, the most connected person in acting is not Mr Bacon. Research by people who found it important enough to do so discovered that the "Center of the Hollywood Universe" shifts over time -- but typically it will be someone who has appeared in many, many films over a considerable period. During the latter part of his long life and prolific career, for instance, Creator/ChristopherLee was credited on [=IMDb=] as being this. As of July 2023, [[https://oracleofbacon.org/center_list.php the center of the Hollywood universe]] has shifted to Creator/SamuelLJackson, who with a mean score of 2.89828 degrees of separation is fractionally more closely linked to everyone else on average than Creator/EricRoberts is, by a mere 0.0041 degrees. Bacon himself isn't even all that high on the list, typically ranking among the top 600 centers of the Hollywood universe but a fair way behind the likes of, say, Creator/ChristianSlater, Creator/VinnieJones, Creator/GaryBusey or Creator/DianeKeaton.

As a fun diversion, note that as soon as an individual acts with someone whose heyday is a long way removed from their own then they will, at a stroke, be connected to a host of actors from decades earlier or later at just a degree or two of separation. For instance, [[MediaNotes/TheSilentAgeOfHollywood silent-era]] icon Creator/BusterKeaton appeared, late in life, in a 1960 film of ''Literature/TheAdventuresOfHuckleberryFinn'' with child actress Patty [=McCormack=] -- who, 48 years later, appeared in ''Film/FrostNixon'' with... Kevin Bacon, giving Keaton a Bacon Number of just 2. In 1989 Bacon starred in ''Film/TheBigPicture'', in which he appeared with Creator/JuneLockhart (b.1925), who made her film debut in ''Film/AChristmasCarol1938'', which featured Lionel Braham (b.1879) as the Ghost of Christmas Present.[[note]](Plus an uncredited Halliwell Hobbes, b.1877.)[[/note]] Lockhart's most recent credited film role was in 2016; Braham's first was in 1915. In 2023's ''Leave The World Behind'', meanwhile, Bacon played the father of 10-year-old Alexis Rae Forlenza -- who, born in UsefulNotes/TheNewTens, therefore has just 3 degrees of separation from actors born in the 1870s...!

!! Average Bacon Number
Researchers have demonstrated (true story!) that almost everyone has a Bacon Number less than 10, due to Kevin Bacon at one point or another appearing in movies with people who've appeared in movies with people who've appeared in movies ''(... etc.)'' with people who've appeared in, mathematically speaking, almost every film on the planet. The Oracle of Bacon claims that 21 persons on TMDB have Bacon Numbers of 10, the highest listed, but does not say who they are.

The perhaps surprising thing is that the average Bacon Number across ''every single person'' in the database, no matter how obscure, is just a little under '''3.1'''. When you stop to think about it, though, it quickly becomes apparent why.

Over the several decades of his career Kevin Bacon has appeared in productions which, put together, feature over 2100 distinct co-stars -- by which we mean everybody with even a tiny onscreen role in them. Even if they never shared a scene with him, each and every one of them has a Bacon Number of 1.

And between them those couple of thousand people link to a couple of ''hundred'' thousand other people who have acted in films with at least one of them, but not with Bacon himself -- each of whom therefore has a Bacon Number of 2. Then at one step further removed, there are over ''680,000'' actors who have at some point appeared alongside one (or more) of those #2s although never alongside a #1 or Bacon himself, making a B.N. of 3 tremendously common.

Now here's the interesting bit. Beyond that, since the possible routes back to Bacon increase exponentially, the number of people with a B.N. of 4 immediately drops sharply to back around the 250,000 mark... and at a B.N. of 5 it collapses to only 32,000, then at 6 to barely 5000 and at 7 to less than a thousand individuals. Because, naturally, once you've got around 1 million more closely connected actors already accounted for, and can map every pathway between them, it swiftly becomes almost impossible for a film actor to have ''never'' worked with anyone in the business who's ever worked with anyone who's worked with anyone who's worked with anyone who's worked with Kevin.

Ironically, Kevin Bacon did not have anything at all to do with the movie ''Film/SixDegreesOfSeparation''.[[note]](However, Creator/DonaldSutherland featured in that movie, and he appeared with Kevin Bacon in ''Film/AnimalHouse'' -- meaning ''Six Degrees Of Separation'' is at two degrees of Kevin Bacon!)[[/note]]

This is all [[JustForFun just a silly game]], of course. Yet those mathematics associated with it have genuine real-world implications -- see the bottom of this page.

!! Similar numbers in other fields
Scientists also have a similar ranking called the Erdős Number, based on co-authorship of mathematical articles with deceased mathematician Paul Erdős. Inevitably there's a combination, the Erdős-Bacon number, based on adding the two together. Thanks to the documentaries, and occasional extra work on math-related films, some mathematicians have EB numbers as low as 3. More surprising are actors who attack the problem from the other side. Danica [=McKellar=] (Winnie from ''Series/TheWonderYears'' and bona-fide mathematician) and Creator/NataliePortman (wrote a psychology paper at Harvard with an Erdős link) each have Erdős-Bacon numbers of 6. (This ties them with UsefulNotes/RichardFeynman.)

There is also now the Sabbath Number, based on how many collaborations it takes to get from a given musician to Music/BlackSabbath. Then, of course, musicians who've appeared in films have Sabbath-Bacon numbers, and a surprising number of math-geeks turned musos have Sabbath-Erdős numbers. Then, there's the Sabbath-Bacon-Erdős number. The lowest known Sabbath-Bacon-Erdős number is 8, famously held by physicist, ''WesternAnimation/TheSimpsons'' guest star, and Music/PinkFloyd guest vocalist Creator/StephenHawking. Neuroscientist Daniel Levitin and inventor Ray Kurzweil have the same number as well.

TabletopGame/{{Chess}} players have a Morphy number, for Paul Morphy, and TabletopGame/{{Go}} players have a Shusaku number, centered on Honinbo Shusaku. Both of those players died in the late 1800s, but if you're interested in a Stiglitz number of 1, economist Joseph Stiglitz is still alive and publishing.

In professional sports, players are generally connected through teammates, not by playing against other players. [[UsefulNotes/IceHockey Ice hockey]] has the Sillinger number, named after journeyman Mike Sillinger. UsefulNotes/{{Baseball}} players have the Miñoso number, after Minnie Miñoso, who played in five different decades.

Thanks to {{Crossover}}s, even fictional characters aren't exempt from this phenomenon. For video game characters (sometimes overlapping with just fictional characters in general), there's the [[Franchise/StreetFighter Ryu]] [[https://www.fanbyte.com/lists/six-degrees-of-ryu number.]] For TV show characters, there's the [[Series/StElsewhere Tommy Westphall]] number.

On a less specific level, the aforementioned serious research into this phenomenon actually has some importance for fields like sociology and epidemiology. In the modern global world, any living or recently deceased person on Earth can apparently be connected to any other person by an astoundingly short chain of connections. For example, in 2019-2020, the UsefulNotes/COVID19Pandemic spread from China to distant tribes on other continents within a couple of months, simply because statistically there are going to be a handful of people in every major city with a particularly short chain of physical connections to that tribal village.
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