I have a question about the concepts of rotation and revolution - on how they are treated in relativity. Since all motion is relative, a revolution of a planetary body around a central body could also be seen instead as a rotation of the central body w.r.t. a fixed (non-revolving) planetary body. Both points of view should be equally valid. Now, why should properties of any object then depend on its state of rotation or revolution? For example, I am thinking about the concept of static and rotating black holes having different properties. When we identify a rotating black hole somewhere, we could also equally consider it to be static, with us revolving around it, surely? So why should there be any observable difference in properties of such an object, which appears to be the case, when we can flip the notions of static and rotating by using appropriate reference frames? Or, is there some sort of preferred reference frame in the Universe which allows us to determine whether something is rotating or not (e.g. ECIF)? If so, how is that taken into account in relativity?