Six Degrees of Separation

Six degrees of separation is the hypothesis that any two people on Earth are connected by a chain of no more than six acquaintances. The phrase derives from Stanley Milgram's small-world experiments in the 1960s, though his actual findings were more modest: only a fraction of letters reached their targets, and average chain lengths varied by social class and geography. The claim entered popular culture through John Guare's 1990 play and subsequent films, becoming an article of faith about global connectedness rather than an empirical measurement. Whether the six-degree property holds at global scale remains unresolved; what is established is that social networks exhibit small-world topology with short average path lengths.

The persistence of the six-degree claim despite weak empirical support reveals the human preference for neat numerical summaries over the messier realities of social stratification and network fragmentation.