Small world or six degrees of remoteness
Imagine a graph whose tops are all people on the earth, and the ribs are dating. If two people are familiar, there is an edge between the corresponding vertices. The hypothesis of six degrees of remoteness suggests that between any two vertices there is a path no longer than six edges.
The author of the hypothesis is Stanley Milgram, who conducted an interesting experiment in 1967. He wrote several hundred letters to two recipients from Boston and distributed them to random people from two American states. People had to send letters to their friends living as close to the addressees as possible. Only a fifth of the letters reached the addressees. These letters went through an average of six intermediaries. Unfortunately, the result of the experiment can equally be considered both a failure and a confirmation of the theory.
You can read more about popularizing hypotheses and experiments on the English wikipedia en.wikipedia.org/wiki/Six_degrees_of_separation .
What is a social network? This is a subgraph of the graph described above. You no longer need to send letters. The database of any social network contains all the necessary information for the experiment. Habr suggests us to look at the list of friends of the second round. But don’t you wonder how many people are on the third round? And on the sixth?
Why did I write this topic? Because I want to interest authors and owners of social networks. And I want to know the results of such experiments.
PS By the way, on the front page of my circle there is a mention of this hypothesis.