Milgram’s experiments are linked to the small-world phenomenon. Through a series of experiences, Milgram and other researchers proved that human societies have a short average path between different people. How short? There is a theory called Six degrees of separation according to which everyone and everything is six or fewer steps away, by way of introduction, from any other person in the world. It means that through friends of friends you are connected to everyone on the planet, from Justin Bieber to the most remote villages in the Amazonia. On virtual social networks, it’s quite true : on Facebook the average number of acquaintances between two users is 4,74. So it’s not hard to imagine that in little networks like the world of Hollywood, everyone knows everyone. Movie buffs have actually invented a game around that called Six degrees of Kevin Bacon. The rules are simple : you have to find the connections between an actor and Kevin Bacon via the people they both have played with. The person who finds the shortest path wins!