Six degrees of separation—the notion that every person on the planet can reach every other through a chain of about six social ties—has been borne out by the first large-scale study of social networks.
The more than 24,000 e-mail users who participated in the study were randomly assigned one of 18 targets in 13 countries, including a police officer in Australia, a veterinarian in the Norwegian army, and a professor at an Ivy League university. The participants were asked to help relay a message to their target by forwarding it to just one acquaintance whom they regarded as "closer" than themselves to the target.
A total of 384 chains reached their target; the others fizzled out when, for example, a recipient mistook the message for spam or was too busy to forward it to a new person. The successful chains averaged 4.05 e-mails. Taking into account the lengths of the unsuccessful chains, researchers estimate that two strangers are typically connected to each o