According to the relativity theory, there is no difference between two observers moving with respect to each other, they both experience identical laws of physics. However, does the same go for rotation?
An object gains rotational energy when torque is applied to it, and it also exerts forces on other objects depending on its rotational velocity. This has been used in many sci-fi movies, where the space-ship has a rotating part (as in the Martian for example), and the astronauts are able to stand casually in there, due to the force that the rotating part exerts on them. Obviously, that would not work if that part of the ship wasn't rotating. However, how do we know whether it is in fact rotating or not? If we are able to tell whether it is, isn't there an universal rotational stationary frame of reference, to which we have to compare everything that rotates?