 Finally, I want to briefly draw attention to the observer-dependent nature of global Lyapunov exponents in the special theory of relativity. As has been recently demonstrated (Zheng, Misra and Atmanspacher 2003), global Lyapunov exponents change in magnitude under Lorentz transformations, though not in sign—e.g., positive Lyapunov exponents are always positive under Lorentz transformations. Moreover, under Rindler transformations, global Lyapunov exponents are not invariant so that a system characterized as chaotic under SD or Chaos\(_{\lambda}\) for an accelerated Rindler observer turns out to be nonchaotic for an inertial Minkowski observer and any system that is chaotic for a an inertial Minkowski observer is nonchaotic for an accelerated Rindler observer. So along with the simultaneity subtleties raised for observers by Einstein’s theory of special relativity  (see the entry on  conventionality of simultaneity),  chaos, at least under SD or Chaos\(_{\lambda}\), turns out to also have observer-dependent features for pairs of observers in different reference frames. What these features mean for our understanding of the phenomenon of chaos remains largely unexplored. 