Title: quantum mechanics - Observer effect, do this mean literally someone or just any interaction with other matter? - Physics Stack Exchange
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Observer effect, do this mean literally someone or just any interaction with other matter?
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Content: When quantum mechanics was first formulated, the authors started with the mathematical definition of a 'measurement', namely projecting the wavefunction of the system on to a certain eigenvector. Since then, there have been attempts to understand what (if any) physical acts correspond to this mathematical definition. We have come up with some cases where what we are doing, physically, clearly does fit the mathematical definition, but still have not found a rule for classifying all actions as either 'measurements' or 'not measurements'. I would say that the basic problem is that quantum mechanics is, at its core, a mathematical formalism. Trying to understand that formalism through intuition has always been a challenge and this includes understanding it through the concepts of language (like 'measurement' and 'observer'). This remains an unsettled problem because from the physicists view it simply isn't important. Not knowing what counts as a measurement and what doesn't turns out to not matter much. We can do all the calculations we care to without making the distinction. You can read more about this if you like; Wikipedia is a good place to start: