Anything and everything in the world is connected to each other.
6 Degrees of Separation
That is what this theory says basically: everyone and anyone in the world are connected to each other. So, according to this theory, you are connected to the poorest and the richest person in the world, your favorite actor, your favorite singer and the person you admire the most through six individuals or less. This theory works by a chain of "friend-of-a-friend". In layman's terms, you know a person who may know a person, who may know a person, who may know a person, who in turn may know a person, who may that richest/poorest person in the world. You are connected to the President of the United States, or the President of any country for that matter, all through six persons or less.
It is not to say that the theory is entirely accurate. No, of course there are some errors. A few examples of this phenomenon today would be the following.
62 Degrees of Wikipedia
This is my favorite one. We all love browsing Wikipedia, right?. Say you open an article about computers. You see a fascinating blue-colored word which you click on and it leads you to a whole new article about that fascinating blue-colored word. You start reading that article, it's just good enough to hold your attention. So, you read that article. Suddenly, another fascinating blue-colored word catches your eye! You feel almost compelled to click that word. Which you do, and it leads you to a whole new article filled with fascinating blue-colored words for you to click on. I mean, who doesn't love Wikipedia?
If we apply the six degrees of separation theory to Wikipedia, we get an interesting result. The game here revolves around reaching the Philosophy article on Wikipedia by clicking the first clickable word on every Wikipedia article in 36 clicks or less.
Basically, let's say you open a random article. You click on the first clickable word of that article, which brings you to a new article, of which the first non-parenthesized, non-italicized clickable word is clicked by you. You keep doing this until you reach the Philosophy article which is usually gotten to in 36 clicks or less.
Of course, like the main concept itself, this game also has some flaws and loopholes. Sometimes, the chain of articles in which you delve have a dead-end. They either lead to an article which has no outgoing links to Wikipedia articles, or contain links to pages that do not exist, or you get stuck in loops.
Six degrees of separation theory was widely popularized by a college game of a similar name called Six Degrees of Kevin Bacon.
Six Degrees of Kevin Bacon
As frequent movie watchers, me and my friends often play this game. Basically, you try to link an actor to Kevin Bacon even if that actor hasn't ever appeared in a movie with Kevin Bacon himself. You do it through a chain of actors, like that friend-of-a-friend chain. Actors are assigned "Bacon numbers" depending upon how far away they are from having appeared in a movie with Kevin Bacon.
Personally, I find this concept to be very fascinating. To think that everyone and everything is just a few steps away is just mindblowing. Almost unbelievable, really. To think that we live in such a small world, pretty crazy right?
For example, President Obama has a Bacon number of 2. He has not ever appeared in a movie, documentary or TV show with Bacon himself, but he appeared with Tom Hanks in The Road We've Traveled. Hanks appeared with Kevin Bacon in Apollo 13. So, Tom Hanks has a Bacon number of 1 while Obama has a Bacon number of 2.