Ever heard of the game Six Degrees of Kevin Bacon? If you haven't, it works like this: Every actor gets a Kevin Bacon number. Kevin Bacon has a Kevin Bacon number of 0, actors who were in a movie with Kevin Bacon get a Kevin Bacon number of 1, actors who were in a movie with someone who has a Kevin Bacon number 1 get a 2, and so on (Everybody always gets the smallest number possible, so if you were in a film with two people, one with a 4 and one with a 6, your Kevin Bacon number would be 5).

The same idea could apply to the articles Wikipedia. Instead of taking "in the same film" as the relation, you can take "is linked to by". We'll call the "Kevin Bacon number" from one article to another the "distance" between them. It's then possible to work out the "closeness" of an article in Wikipedia as its average distance to any other article. I wanted to find the centre of wikipedia, that is, the article that is closest to all other articles (has minimum closeness).