  The 'out of the blue' nature of recent terror attacks and the diversity of
apparent motives, highlight the importance of understanding the online
trajectories that individuals follow prior to developing high levels of
extremist support. Here we show that the physics of stochastic walks, with and
without temporal correlation, provides a unifying description of these online
trajectories. Our unique dataset comprising all users of a global social media
site, reveals universal characteristics in individuals' online lifetimes. Our
accompanying theory generates analytical and numerical solutions that describe
the characteristics shown by individuals that go on to develop high levels of
extremist support, and those that do not. The existence of these temporal and
also many-body correlations suggests that existing physics machinery can be
used to quantify and perhaps mitigate the risk of future events.
