Interested in opinions: What is a measurement in QM? I.e. what is needed to make a wavefunction "collapse" and for an instant moment not obey the Schrödinger equation? Could this "not evolving according to S.E." be a clue that the macroscopic laws of nature can't (in principle) be derived directly from QM, but there has to come in something else between? (I know there are some respected scientist (can't remember names) who are saying that there may be something "between", but I don't know what they are basing that on.) Before going deeper, I would like to hear what you count as a "measurement"?