Absolute quantum mechanics (Q2755346)

Though Newton believed in what he called `absolute spacetime', classical mechanics may be formulated without it. Indeed, it may be formulated in a way that does not make reference to unobservable quantities like absolute positions and velocities. Still, what is or is not observable is a matter of much debate. At a minimum, it would seem that relative positions and velocities are observable, where `relative' could mean `relative with respect to an observer'. Such an interpretation has thus been called `the relational approach' to the classical theory of measurement and is widely accepted. The question Weinstein raises is: what will count as a quantum analogue of such a theory? since quantum mechanics, as opposed to its classical counterpart, seems to require absolute space and time. He argues that the tenacity of absolute spacetime in the quantum world is a result of the fact that most of us do not know how to extract observable content in the absence of any notion of measurement making reference to classically described measuring devices which occupy certain spacetime points. Thus, it is the hybrid classical/quantum description of measurement that stands in our way. Weinstein expresses his hope as: ``further progress in understanding quantum theory will come, not by probing quantum theory proper, but by coming to understand how to move beyond it''. The reader should add a question mark to the title.