The internet has a Kevin Bacon number: 19

Posted by Emma Woollacott

The internet is less sprawling than you might think: through its own 'Kevin Bacon effect', it seems every page is connected to every other by no more than 19 clicks.

All the people on the planet, so the theory goes, are separated by just six links. But with rather more internet pages than people - 14 billion and counting - it takes a little longer to get from one to another.

To reach this conclusion, detailed in a Royal Society paper, Hungarian physicist Albert-László Barabási created a simulation of the web. And, he discovered, the vast majority of pages, images and other web documents are connected only to a very few others.

What makes the difference is the few that aren't - search engines, indexes, aggregators and the like. Some of these might not immediately spring to mind - the eHarmony dating site, for example.

These act as hubs, dramatically increasing the level of connectedness. This, plus the fact that the internet tends to be organized by factors such as subject matter and geographical region, means that the same 19-click rule could continue to apply, however large the internet grows.

There is, unfortunately, a downside to this. It means that cybercriminals can in theory knock out large parts of the web, as long as they can get access to the comparatively small number of nodes that are the most interconnected. Let's hope eHarmony has really tight security.