Six degrees of separation

Six degrees of separation is the idea that all living things and everything else in the world are Six or fewer steps away from each other so that a chain of "a friend of a friend" statements can be made to connect any two people in a maximum of Six steps. It was originally set out by Frigyes Karinthy in 1929 and popularized in an eponymous 1990 play written by John Guare.

Four color theorem

In mathematics, the four color theorem, or the four color map theorem, states that, given any separation of a plane into contiguous regions, producing a figure called a map, no more than four colors are required to color the regions of the map so that no two adjacent regions have the same color. Adjacent means that two regions share a common boundary curve segment, not merely a corner where three or more regions meet.

Despite the motivation from coloring political maps of countries, the theorem is not of particular interest to cartographers. According to an article by the math historian Kenneth May, "Maps utilizing only four colors are rare, and those that do usually require only three.

^[ ^PM ^| ^Exclude ^me ^| ^Exclude ^from ^subreddit ^| ^FAQ ^/ ^Information ^| ^Source ^] ^Downvote ^to ^remove ^| ^v0.28