Six Degrees of Separation

Six degrees of separation (also referred to as the "Human Web") refers to the idea that, if a person is one step away from each person they know and two steps away from each person who is known by one of the people they know, then everyone is at most six steps away from any other person on Earth. It was popularized by a play written by John Guare.

六度分隔的现象，并不是说任何人与人之间的联系都必须要通过六个层次才会产生联系，而是表达了这样一个重要的概念：任何两位素不相识的人之间，通过一定的联系方式，总能够产生必然联系或关系。显然，随着联系方式和联系能力的不同，实现个人期望的机遇将产生明显的区别。

A Facebook platform application named “Six Degrees” has been developed by Karl Bunyan (London network), which calculates the degrees of separation between different people. It has about 5.2 million users (as of July 31, 2009), as seen from the group's page. The average separation for all users of the application is 5.73 degrees, whereas the maximum degree of separation is 12. The application has a "Search for Connections" window to input any name of a Facebook user, to which it then shows the chain of connections. As of July 26, 2009, the application is no longer available.