Six degree of separation

Six degrees of separation is the hypothesis that anyone on Earth can be connected to any other person on the planet through a chain of acquaintances with no more than 5 intermediaries.

The latest proof of this hypothesis - in 2001 Duncan Watts, a professor at Columbia University, used an e-mail message as the "package" that needed to be delivered, and after reviewing the data collected by 48,000 senders and 19 targets (in 157 countries), Watts found that the average number of intermediaries was, 6.