Heisenberg proposed that observation of a particle could never be completely accurate as to both position and velocity. The Copenhagen interpretation proposed that this uncertainty is a feature of the particles themselves--that they are basically probability functions. Neither challenges Realism, since for a Realist mathematical laws, like probability, are just as real as physical objects (or even more real than they are). As for "the states of particles [being] observer dependent in a very deep way," whatever "a very deep way" may mean, the fact remains that virtually none of the virtually infinite quantity of particles in the past, present, and future universe[s] can be in an "observer-dependent" state in any, let alone an "important" or "deep" sense, since they are in no sense whatever capable of observation through any conceivable experimental apparatus.
> > > The hard case for realism even on the NOA is
>> quantum
> > > mechanics. There the science itself sure as hell seems
> > > to tell that what there is, is in an important way
> > > observer-dependent.
Shane Mage
"When we read on a printed page the doctrine of Pythagoras that all things are made of numbers, it seems mystical, mystifying, even downright silly.
When we read on a computer screen the doctrine of Pythagoras that all things are made of numbers, it seems self-evidently true." (N. Weiner)