Edit- the answer is mach's principle and mach's principle is sketchy so there is no good answer.
So I understand that centrifugal force is really just inertia and stuff but I still have a question. In a sci-fi movie, a spaceship is shown rotating to generate artificial gravity as it flies through space. If you rotate the camera with the spaceship, it doesn't appear to be rotating and there wouldn't appear to be a centrifugal force. So what is the frame of reference for if a spaceship is rotating? I picture a spaceship launched from earth. It doesn't rotate so the astronauts float around and stuff. The spaceship then flies through the cosmos, without rotating, and parks itself above a rapidly spinning planet. The astronauts still think the planets rotating, not them, but any aliens looking up would be puzzled by the fact that despite the rapid rotation, no centrifugal force happens. There may not be a universal reference for movement, but is there one for rotation? If astronauts have mass and are spinning in circles with the spaceship, wouldn't their inertia fling them outwards?
