The story of how Kenna and Mac Carron got here begins with the Irish tale of the cattle-raid of Cooley, or the Táin Bó Cúailnge. That yarn tells how the warrior-queen Medb of Connacht rallies an army to steal a fine bull from Ulster, and how youthful Cúchulainn, an Ulster folk hero, stands against her. Complete with a maiden prophet with three pupils in each eye, wild chariot rides, and an enormous cast of characters, it's a story to grip anyone's imagination.

It's a story that Kenna and Mac Carron, who are both Irish, have known since childhood. Several years ago, Kenna, who has a successful career as a physicist, found his thoughts returning to mythology. It wasn’t as big a departure as it might seem at first. "In statistical physics, you're dealing with objects such as gasses that are comprised of molecules and atoms," he says. "The system consists of many small entities, and so many of them you cannot deal with them individually, you have to deal with them statistically." Some physicists have started to use similar methods to look at how large numbers of people interact to produce aspects of human society, and Kenna wondered whether they could be applied to myths and stories. The Táin, which comes to us in pieces from many different manuscripts, the oldest nearly 1,000 years old, is considered literature rather than historical account. But it might still encode, in a way statistics can reveal, information about the society that produced it. Math might also help classify tales in a new way, quantitatively, in addition to the usual qualitative classifications.

In thinking these thoughts, he had plenty of company — the idea that computation might be able to provide insight into literature and history has gathered speed in the last couple of decades. But it has provoked some controversy, as researchers try to figure out how computer science and statistics can be helpful in fields where trained reading and intuition are central. There are many levels of the debate, but it usually circles around to this point: Can you answer valuable questions this way? Can these tools provide information that is hard to grasp otherwise?

Math might help classify tales in a new way: quantitatively

It's easy, it turns out, to do this badly. Siccing a pattern-finding program on a novel might uncover meaningless patterns, or ones so obvious that a high school freshman could see them. But Tim Tangherlini, a folklorist and professor at UCLA who hosted a 2010 National Endowment for the Humanities meeting on network analysis, sees potential. "There are a lot of latent patterns in this material that you can't discern overtly. You can do it very well as a trained reader — by developing ways of thinking about the material that let us see latent patterns — but we have a very hard time articulating it." Algorithms could help make those patterns visible. In the case of social networks, they can reveal which people are the most connected or powerful, as well as how densely connected the network is and the average distance between any two people, qualities that vary depending on the type of group.

For instance, research suggests that real social networks have different properties than fictional ones. The idea of seeing where epics — which are certainly not all fact, but perhaps not all fiction — fell on that spectrum appealed to Kenna, who brought Mac Carron on to work on the project. In 2010, with funding from the Leverhulme Trust, Mac Carron went through the Táin, Beowulf, and The Iliad, noting each time a character appeared and each time he or she interacted with someone. Eventually he had a map of the social networks in each story that he could compare against information about real-world networks that other researchers had built of groups like scientists, jazz musicians, and film actors.

Perhaps the 'Táin' is not as fantastical as its reputation would suggest

What Kenna and Mac Carron found was that the epics fell between the real networks and the fictional ones. The network in The Iliad is relatively realistic, and Beowulf's also has realistic aspects, with the exception of the connections to Beowulf himself. That chimed with the idea from the humanities that he, unlike some others in the story, may not have existed. The Táin's network was more artificial. Interestingly, however, they found that a lot of the Táin's unreality was concentrated in just a few, grotesquely over-connected characters. When they theorized that some of those characters might actually be amalgams — for instance, that some of the times the queen of Connacht is said to speak to someone, it might be a messenger speaking for her instead — the network began to look more realistic. At least from a social network perspective, perhaps the Táin is not as fantastical as its reputation would suggest, the researchers proposed. That doesn't mean the events really happened, or that the people are real. But it raises the question of why the network looks the way it does.