THERE’S a game that movie buffs and students play in the US which involves linking the actor Kevin Bacon to any other actor in the American movie industry.

You have to find the links using movies. For example, it only takes three movies to link Kevin Bacon with Charlie Chaplin. (Kevin Bacon was in a movie called Quicksilver with Laurence Fishburne, who was in Apocalypse Now with Marlon Brando, who was in the Countess of Hong Kong with Charlie Chaplin).

It turns out that there are (or were) over 200,000 actors in the US and analysis has proven that the maximum number of movies between all of them is four. Isn’t that astonishing? This proves that the movie industry is a Small World.

Small World Theory – otherwise known as the Six Degrees of Separation (the movie game is actually called the Six Degrees of Kevin Bacon) – was until a few years ago confined to pub conversations.

It is now a major area of study and many academics believe that the phenomenon can explain things as diverse as the spread of ideas to how the human brain works.

What Small World theory seeks to explain is how networks interact. The idea proposes that if you sought at random an Indian beggar in the middle of the state of Uttar Pradesh, then you are only five relationships between you and him. Can this be true?

The model would work something like this. Of all the people you know, one is interested in third world development. This person knows someone who worked in India. In turn they know a man from Uttar Pradesh and so on.

All the studies conducted show that the theory is indeed correct. On the internet there are trillions of web pages. Yet every single page can be accessed from every other page by a maximum of 19 clicks.

OK, so it’s true – but does it matter?

Small World Theory and the understanding of it can probably allow the global community to start fixing all the sundered relationships in the global village. That’s a big ask but critical to our decision-making processes is the reality that everything is interconnected.

Small World Theory can illuminate other recent concepts such as Chaos Theory and the Tippling Point. You can see how social change can spread like wildfire – you can see the threat to diversity. Islamic fundamentalism can be better understood as a reaction to super-rapid cultural changes. Conflict often happens when people find themselves by-passed and powerless.

Then you can factor in the role of international media which accelerates the Small World effect. Billions of us have a media relationship with George Bush and Osama Bin Laden.

Oddly enough, the Small World emphasises the importance of local groups and networks. It explains how a consensus arrived at separately in many pubs can suddenly become national law.

(You can take part in a Small World experiment at smallworld.sociology.columbia.edu)