Absolute rotation and acceleration, did Einstein slay the Hydra?
Force = Mass * acceleration but what is the acceleration relative to? This problem of what determines inertial frames is reflected in the following free translations from Einstein and Mach. There is no inertia of matter against space - there is only inertia of mass against mass. The principle of the relativity of inertia is not fulfilled by the mere
influence of nearby bodies on inertia. The inertia must be entirely so caused. By a stroke of genius Newton invented absolute space so essential to the development of dynamics. It has been an even greater struggle to eliminate absolute space from dynamics - a process that is even now still incomplete.