Mach's Principle: A Response to Mashhoon and Wesson's Paper arXiv:   1106.6036
  In their recent "Mach's principle and higher-dimensional dynamics", Mashhoon and Wesson argue that Mach's principle is not properly incorporated into general relativity and that in Einstein's theory "the origin of inertia remains essentially the same as in Newtonian physics." While it is true that the motion of a single test particle in a Newtonian inertial frame of reference appears essentially the same as in an Einsteinian local inertial frame, this misses the point. The issue is not what motion looks like in an inertial frame of reference but what is the origin of the inertial frame. Unlike Newtonian dynamics, general relativity does implement Mach's principle when considered from this correctly formulated point of view. 
Julian Barbour
gr-qc