Thoughts in a Haystack

Using methods borrowed from statistical physics, the researchers searched for patterns in data describing the numbers of adherents to major religions -- including Christianity, Islam and Buddhism – over the past century. These patterns suggested that the changes in the numbers of religious adherents can be modelled using an "agent-based" approach. Agent-based models assume that the collective behaviour of a group of individuals arises from a set of simple rules that define how an individual interacts with others in the group. This approach has already been used to study a wide range of sociological and physical processes including crystallization.

The researchers then created a model of the time evolution of religions using the agent-based concept of "preferential attachment", which was first formulated in 1999 to explain self-organizing networks such as the World Wide Web. Preferential attachment is the tendency of an individual to form relationships with popular individuals – which are defined as individuals who themselves have relationships with a large number of other individuals.

According to Ausloos, the number of adherents to a specific religion appears to follow a "growth-death law" that also describes how the size of crystalline regions grow and shrink in some materials. One striking similarity to crystallization is that religions can appear almost spontaneously in a process that is similar to the nucleation of crystals – with a popular leader often fulfilling the role of a nucleation point. A recent example of the spontaneous nucleation of a religion is the Church of Jesus Christ of Latter-day Saints (the Mormons), which was founded about 175 years ago in the US by Joseph Smith and now has nearly 13 million members worldwide.

The growth and demise of a religion can also be affected by phenomena such as mass conversions or genocide that affect entire groups -- rather than the interactions between individuals. Ausloos describes these influences as "external fields", in analogy to externally-applied electric fields or temperature gradients that can affect the crystallization process.