By now, most of us have had the experience of being at some relatively far-off location and bumping into a complete stranger, only to find out that they are from the same town as you and know many of the same people as you. Such encounters are usually punctuated by an exclamation of “What a small world!”, or some variant thereof. In the 1970s, Harvard psychologist Stanley Milgrom, building on earlier work by social scientist Ithiel de Sola Pool and mathematician Manfred Kochen, conducted a groundbreaking experiment in social network theory to quantify this small-world phenomenon and found that any two individuals in the USA, in the 1970s mind you, were ‘connected’ to each other by six degrees of separation on average. In order to model this phenomenon, applied mathematician Steven Strogatz and his then PhD student Duncan Watts hit upon the idea of using an arcane branch of mathematics called graph theory to quantify the mechanics of such world networks.