Duncan Watts discusses how the Internet is beginning to lift a long-time constraint of social science research on emergent collective behaviour: the difficulty of measuring interactions between people, at scale, over time, while also observing behaviour. Social science is often concerned with the emergence of collective behavior out of the interactions of large numbers of individuals; but in this regard it has long suffered from a severe measurement problem - namely that interactions between people are hard to measure, especially at scale, over time, and at the same time as observing behavior. In this talk, Duncan will argue that the technological revolution of the Internet is beginning to lift this constraint. To illustrate, he will describe four examples of research that would have been extremely difficult, or even impossible, to perform just a decade ago: using email exchange to track social networks evolving in time; using a web-based experiment to study the collective consequences of social influence on decision making; using a social networking site to study the difference between perceived and actual homogeneity of attitudes among friends; using Amazon's Mechanical Turk to study the incentives underlying 'crowd sourcing'. Although internet-based research still faces serious methodological and procedural obstacles, Duncan proposes that the ability to study truly 'social' dynamics at individual-level resolution will have dramatic consequences for social science.