It kind of reminds me of Mach's principle "There is a fundamental issue in Relativity theory. If all motion is relative, how can we measure the inertia of a bo

It kind of reminds me of Mach's principle "There is a fundamental issue in Relativity theory. If all motion is relative, how can we measure the inertia of a body? We must measure the inertia with respect to something else. But what if we imagine a particle completely on its own in the universe? We might hope to still have some notion of its state of rotation. Mach's principle is sometimes interpreted as the statement that such a particle's state of motion has no meaning in that case." http://en.wikipedia.org/wiki/Machs_principle http://en.wikipedia.org/wiki/Machs_principle