Social scientists have traditionally relied on field surveys and lab experiments for the bulk of their data, but such sources have numerous shortcomings. In particular, surveys offer only indirect evidence of human behaviour while lab experiments tend to be reductive and artificial, failing to stimulate the complexities associated with everyday life. New digital technology has, however, opened up a whole new approach. Sensors, mobile devices and clever algorithms permit the measurement or estimation of a range of properties including interaction times, facial or bodily communications and emotional states. Alex Pentland uses the semantic "reality mining" to describe the study of human behaviour in natural environments by means of such technologies, and refers to the emergent properties and patterns as "social physics". This text is a must-read for all those designers who are active in applications which involve "big data" or "internet of things".