Big ideas are nothing new in physics. Predicting multi-dimensional universes and studying unseen sub-atomic particles are all in a day's workforthe jobbing physicist. But forthe next challenge the physicists are looking closer to home; they hope to be able to predict human behaviour. Quentin Cooper delves into the world of "social physics" and asks whetherthe complexities of society can really be reduced to a few universal laws? Producer Jonathan Fildes