How is it possible that an actress can be shown dancing on the ceiling in a movie?

Answer 1

This is a question involving frames of reference, which is a fundamental concept of physics. Whether it is Lionel Richie, Fred Astaire, or others who have been filmed danding on a ceiling, the trick involves building a room inside a very large cylinder. Then the whole cylinder is rotated. This "trick" dates back almost a hundred years. Picture a room with one wall missing. Now picture this room built into a big cylinder that is lying on its side on rollers. The room is a "trick" room in that everything in it must be "rigid" so that as the room rolls over, nothing in the roome moves. For instance, if a light fixture is hanging from the ceiling of this room, it will have to be rigidly mounted so that it appears to "hang" from the room even when the room is tilted sideways. Anything on the floor, like chairs or other furnature, will all have to be "bolted" to that floor. Pictures won't "hang" on the wall, but will be fastened tightly so they cannot move. Curtains on a window will have to be unable to move in any way or the illusion will be broken. Lastly, rigidly fix a camera that is looking "into" the room through the missing wall. Don't put anyone in the room for now. Look at the room. Now rotate it so it is on its side. You're outside on the floor of the studio, but the room is tipped over 90 degrees. Notice the camera position? It has not changed with reference to the room. The pictue taken by the camera like this, or the one taken when we rotate the whole thing to completely invert the room, will be the same as all the other pictues. From the point of view of the camera, the room is stationary and "upright" all the time. Start with the room right side up, put in your dancer, roll camera and start slowly rolling the room. Now as the whole room moves and the camera moves, the dancer can navigate the floor as it tilts, then shift to the wall, and move on to the ceiling, the last wall and back to the floor. All the while the room is "right side up" in the camera lens.