Models are simplifications/approximations made on purpose, as in "I know this is wrong on some level, but it's close enough for my use case", or "this makes the maths solvable".
> Quantum physics is a theory, as in "as far as we can tell, this is an exact mathematical description of the world".
Is it?
If by "mathematical exactness" you merely mean we have somehow been able to produce some numbers that later on we measured in experiments, then yes. (Though we haven't been able to produce such numbers in all cases, see e.g. [0].)
I my book, though, mathematical exactness means your model is mathematically consistent and is applied with the necessary mathematical rigor.
Quantum mechanics and quantum field theory, as they are commonly taught in universities, are everything but. They are a bunch of concepts and recipes that, albeit successful, are held together loosely with duct tape and lots of hand waving to make you ignore the logical gaps & jumps and the fact that many of the "mathematical" objects physicists refer to don't even exist[1]!
[0]: https://www.scientificamerican.com/article/this-simple-exper...
[1]: Haag's Theorem, Aizenman–Fröhlich Triviality Theorem, etc.
What a theory is, is more like a model (or maybe meta-model) with a particularly broad scope or high explanatory value, often a mathematical framework that gives a common foundation and theoretical justification for multiple experimentally-derived models.
Quantum electrodynamics is a quantum theory. Quantum chromodynamics is a quantum theory. String theory is a quantum theory. I'm sure there is a correct quantum theory of gravity - we just don't know what it is yet.
... which "we think" is functioning that way not to mention that theory itself might be wrong and be replaced as most of the supporters of quantum theory doesn't seem to look on it as something that explain mechanics of it, but rather how magic of "unexplainable" quantum mechanics works.
Heck your descriptions of a model is also what we would call an effective theory (i.e. a description valid for a specific range of parameters/scale).
I don't think there's a commonly agreed difference between model and theory and I sure have heard many physicists use them interchangeably when it suits them (and I'm guilty of it myself). Perhaps theory feels 'wider', as in quantum theory encompasses models for many quantum systems, but that's as far as I'd go.
> [...] when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical, they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together.
> All models are wrong
That famous quote could use attribution: https://en.wikipedia.org/wiki/All_models_are_wrong
> If you make the error of believing that quantum mechanics is ontological god’s honest truth of nature
This is why science & experiment exists. The author holds no such belief, and the paper makes that very clear. That is what he actually meant by “I Don’t Understand Quantum Physics”. Jump to the very last section, “Is Quantum Theory Correct and Complete?” He’s pointing out the confusing and contradictory nature of the model so far, and saying that Quantum is incomplete and needs work. He is not making any category error.
It could, but doesn't need it.
That models are not direct truth is just logical. If there were such a thing that were indistinguishable from the direct truth, it would be the direct truth, not some other thing called a model.
This is why I've never understood the "revalatory" nature of Godel's incompleteness. Of course any axiomatic system must not contain all truths. Axiomatic systems are models and models can't contain all truth. If an axiomatic system contained all truth it would just be all truth rather than some other thing called an axiomatic system.
The only case in which Godel's argument surprises is the case in which one has a fundamental misunderstanding of what a model can and cannot be, which I suppose must have been more common in his time, but I was really confused when my highschool teacher went to great lengths to explain that a model cannot contain the whole truth because...of course it can't?
If obvious, can you prove it without reading Gödel’s proof or anyone else’s?
The important (2nd) part of Gödel’s proof is not that a model can’t contain all truth, it’s that a model cannot prove itself true, which is a far stronger statement than the intuition you describe. Of course, belief that your own intuition is independent of history is also highly questionable; you were raised and educated in an environment in which people were already aware of Gödel. It’s like saying the number zero is obvious (which it is now) despite the fact that it took thousands of years before it was used formally as a number. There was a time when it wasn’t obvious to the smartest people alive.
Note that formal axiomatic systems aren’t physical systems; what Gödel was talking about and what George Box was talking about are related but somewhat different concepts. It is obvious in physics that a parabolic ballistic trajectory model doesn’t account for air turbulence. It’s not at all obvious that all of math itself is guaranteed to produce contradictions and cannot prove itself, especially if you’re allowed to change math or use any system you want.
I also think you can be a realist without having to make the jump to ontological irreducibility. You can say that our latest theory is a better approximation than the previous one and the previous one was an approximation as well.
Penrose has fallen into the same logical fallacy that many older, retired theoretical physicists have (notable einstein?).
Sure, but what if you don’t understand the model?
Quantum mechanics is a framework for how theories are built, not a specific theory, and it's really all or nothing. There's not much between the quantum and classical ways of viewing the world.
But it just turns out that there's a limit in which the quantum world looks approximately classical.
But as a physicist I have no illusion that any of our theories are actually true. They are all models that help us making sense of an unimaginably complex universe.
0. Special Relativity is already baked into the Standard Model, which is a quantum theory. It's General Relativity that causes problems.
what about gravity? If we don't know the correct account of that, how can we know those are exactly correct?
So we really are stuck with quantum mechanics, and there must be a quantum theory of gravity. In fact, there are actually quantum theories of gravity (including String Theory), but we don't know whether they're the correct theory that describes our universe.
...unless I have understood it otherwise, but quantum mechanics is still an approximation of things we simply are unable to measure individually - mostly because of speed and have to resort to guessing that approximation of that limited time period, which is still too long. It would be the same as trying to guess position of a ship during voyage across the ocean and taking the smallest measurable time period as 100 years, in which the ship has been already sunk out of existence, while smaller time period would have given us better picture and quantum mechanics that we are able to use has exactly that issue - we are unable to measure and record particles at smaller time intervals. At best we can see trajectories of particles long gone.
Also, this book is not agreeing with your statement, to me which sounds like Religion(because you have no explanation at all!) and should not be part of Science.