Proper frame

A proper frame, or comoving frame, is a frame of reference that is attached to an object. The object in this frame is stationary within the frame, which is useful for many types of calculations.

For example, a freely falling elevator is a proper frame for a free falling object in the elevator, while the surface of the Earth is not.

Proper frames can be inertial as well as non-inertial as in the example above.

The use of a proper frame is essential for the investigation of physical laws within the framework of general relativity.

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