"The original “six degrees” finding, published in 1967 by the psychologist Stanley Milgram, was drawn from 296 volunteers who were asked to send a message by postcard, through friends and then friends of friends, to a specific person in a Boston suburb. The new research used a slightly bigger cohort: 721 million Facebook users, more than one-tenth of the world’s population. (...) The experiment took one month. The researchers used a set of algorithms developed at the University of Milan to calculate the average distance between any two people by computing a vast number of sample paths among Facebook users. (...) “It’s the weak ties that make the world small.” (...) - Amira