Ok, so I'm having trouble imagining why a "centrifugal force" would exist for a rotating space station. As I understand it if there was only vacuum inside the station then anyone inside it would not move toward the "floor" (outer wall), so I can only imagine that it would be the air inside the station pushing everyone outwards. If this is the case, would there be much force at all acting on anyone inside? Also this is similar to a question I have for a rotating bucket of water. Is gravity required in the first place for the water to stay in the bucket if swung vertically?