# Science behind Six Degrees of Kevin Bacon

Boffins playing studying 'Six Degrees of Kevin Bacon' think the science behind it could have a massive impact on society.

No longer is the game - where players try to connect any film actor in history to Kevin Bacon - just a bit of dinner-party fun, now it counts as science.

The game is said to rely on a phenomenon called the "small-world paradigm" which links two people in a social network.

But now the boffins from the University of California have found a mathematical model called "hidden metric space" that may explain both social and natural networks and eventually be able navigate them.

According to the researchers, natural networks transmit signals or messages with a high degree of efficiency, even though no single node can visualize the structure of the entire network.

But by constructing a mathematical model of geometry underlying the topology of these networks, the researchers discovered that many complex networks share a similar global topological structure (or shape.)

Dmitri Krioukov, lead researcher said: "When you know the network topology, you merely know the basic layout of a network. But when you discover its underlying geometry, or hidden space, you may know how this complex network really functions."

Caption: How the hidden metric space guides communication. If node A wants to reach node F, it checks the hidden distances between F and its two neighbors B and C. Distance CF (green dashed line) is smaller than BF (red dashed line), therefore A forwards information to C. Node C then performs similar calculations and selects its neighbor D as the next hop on the path to F. Node D is directly connected to F. The result is path ACDF shown by green edges in the observable topology.

Looking at 'small-world phenomenon' and 'Six Degrees of Kevin Bacon' the researchers say: "The only information people possessed to make their routing decisions was a set of descriptive attributes of the destined recipient – his or her home base and occupations.

"People then determined who among their contacts was "socially closest" to the target. For aficionados of the Kevin Bacon game, the goal was to connect any actor in Hollywood to Bacon through the films he made."

The researchers think their results could even help remove bottlenecks from the internet and biological systems.

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Picture credit: CAIDA, San Diego Supercomputer Center, UC San Diego.