  However, what does appear to pass as a crucial feature of chaos for Batterman—a definition if you will—is the presence of a kind of “stretching and folding” mechanism in the dynamics (see the discussion on p. 49 and figure 5 of his essay). Basically such a mechanism will cause some trajectories to converge rapidly while causing other trajectories to diverge rapidly. Such a mechanism would tend to cause trajectories issuing from various points in some small neighborhood of state space to mix and separate in rather dramatic ways. For instance, some initially neighboring trajectories on the Lorenz attractor (Figure 1) become separated, where some end up on one wing while others end up on the other wing rather rapidly. This stretching and folding is part of what leads to definitions of the distance between trajectories in state space as increasing (diverging) on average. 