Why did physicists start using the word “real” and “realism”? It’s a philosophical term, not a physical one, and it leads to a lot of confusion. “Local” has a clear physical meaning, “realism” gets confusing. I have seen some papers that use “realism” in a way that has a clear physical definition, such as one I came across defined it in terms of a hidden variable theory. Yet, I also saw a paper coauthored by the great Anton Zeilinger that speaks of “local realism,” but very explicitly uses “realism” with its philosophical meaning, that there is an objective reality independent of the observer, which to me it is absurd to pretend that physics in any way calls this into account.
If you read John Bell’s original paper “On the Einstein Podolsky Rosen Paradox,” he never once use the term “realism.” The only time I have seen “real” used at all in this early discourse is in the original EPR paper, but this was merely a “criterion” (meaning a minimum but not sufficient condition) for what would constitute a theory that is a complete description of reality. Einstein/Podolsky/Rosen in no way presented this as a definition of “reality” or a kind of “realism.”
Indeed, even using the term “realism” on its own is ambiguous, as there are many kinds of “realisms” in the literature. The phrase “local realism” on its own is bound to lead to confusion, and it does, because I pointed out, even in the published literature physicists do not always use “realism” consistently. If you are going to talk about “realism,” you need to preface it to be clear what kind of realism you are specifically talking about.
If the reason physicists started to talk about “realism” is because they specifically are referring to something that includes the EPR criterion, then they should call it “EPR realism” or something like that. Just saying “realism” is so absurdly ridiculous it is almost as if they are intentionally trying to cause confusion. I don’t really blame anyone who gets confused on this because like I said if you even read the literature there is not even consistent usage in the peer-reviewed papers.
The phrase “observer-dependence” is also very popular in the published literature. So, while I am not disagreeing with you that “observation” is just an interaction, this is actually a rather uncommon position known as relational quantum mechanics.
This is only true if you operate under a very specific and strict criterion of “realism” known as metaphysical realism. Einstein put forward a criterion of what he thought this philosophy implied for a physical theory, and his criterion is sometimes called scientific realism.
Metaphysical realism is a very complex philosophy. One of its premises is that there exists an “absolute” reality where all objects are made up of properties that are independent of perspective. Everything we perceive is wholly dependent upon perspective, so metaphysical realism claims that what we perceive is not “true” reality but sort of an illusion created by the brain. “True” reality is then treated as the absolute spacetime filled with particles captured in the mathematics of Newton’s theory.
The reason it relies on this premise is because by assigning objects perspective invariant properties, then they can continue to exist even if no other object is interacting with them, or, more specifically, they continue to exist even if “no one is looking at them.” For example, if you fire a cannonball from point A to point B, and you only observe it leaving point A and arriving at point B, Newtonian mechanics allows you to “track” its path between these two points even if you did not observe it.
The problem is that you cannot do this in quantum mechanics. If you fire a photon from point A to point B, the theory simply disallows you from unambiguously filling in the “gaps” between the two points. People then declare that “realism is dead,” but this is a bit misleading because this is really only a problem for metaphysical/scientific realism. There are many other kinds of realism in literature.
For example, the philosopher Jocelyn Benoist’s contextual realism argues that the exact opposite. The mathematical theory is not “true reality” but is instead a description of reality. A description of reality is not the same as reality. Would a description of the Eiffel Tower substitute actually seeing it in reality? Of course not, they’re not the same. Contextual realism instead argues that what is real is not the mathematical description but is precisely what we perceive. The reason we perceive reality in a way that depends upon perspective is because reality is just relative (or “contextual”). There is no “absolute” reality but only a contextual reality and that contextual reality we perceive directly as it really is.
Thus for contextual realism, there is no issue with the fact that we cannot “track” things unambiguously, because it has no attachment to treating particles as if they persist as autonomous entities. It is perfectly fine with just treating it as if the particle hops from point A to point B according to some predictable laws and relative to the context in which the observer occupies. That is just how objective reality works. Observation isn’t important, and indeed, not even measurement, because whatever you observe in the experimental setting is just what reality is like in that context. The only thing that “arises” is your identification.