Nonlinear dynamics: Chaos in space and time

Many aspects of nature are essentially unpredictable over the long term, even when quantum effects are completely absent. A frequent cause is chaotic dynamics, which can arise when the rates of change of important dynamical variables depend in a nonlinear fashion on the variables themselves. Famous examples are the unpredictable behaviour of the weather and of populations of organisms. Chaotic temporal dynamics has now been documented in practically every scientific discipline — the fascination for both scientists and the public is that chaos helps us understand what can be predicted about the systems we study, and what cannot. But our understanding of chaos in most systems found in nature, which are complex in both space and time, is relatively limited. On page 733 of this issue, Egolf et al. analyse the chaotic space and time variations of a heated fluid in a way that could eventually be applied to natural systems such as the weather.