How does relativity accounts for rotaional motion, which is a non inertial reference frame? How does relativity responds to Newton's thought experiment to prove the existence of absolute space? He argued that the curvature of the water inside a rotating bucket, demonstrates the true motion of the water in reference of what must be absolute space. (he used a similar thought experiment using two spheres conected by an ideal rope in an empty universe. If these spheres rotate, a tension force is created on the rope, which indicates the "real movement" in reference to absolute space).