A FLOCK of thousands of birds suddenly banks, as if on cue. In smooth-flowing traffic a jam suddenly clogs the roads. In a bustling crowd, a stampede erupts, seemingly from nowhere. It may now be possible to detect the subtle precursors to such phase transitions, and so take steps to avoid the undesirable ones.
A phase transition is a transformation in a system’s organisation, such as liquid water freezing to solid ice. Such transitions are routine in nature, and reflect a sudden reorganisation of atoms or molecules, but predicting exactly when they occur was thought to require information about most…
