Frames, measurements and field variables
Both experimental and theoretical physics pay tribute to the notion of frame. Position and/or motion of a body can only be described with respect to a certain frame. From the experimental point of view, the frame is given by a system of bodies – or, in a more abstract manner – of points relatively fixed with respect to each other that intermediate measurements of distances and directions. Interference of the speculative thinking made then possible to detach the notion of coordinates of a point in a given frame: spatially, the point is localized by three real numbers – its coordinates – and, if it moves, also by the time moment determined by an horology attached to the point when its localization is determined (for details see -).