Crazy. It does that a lot - some notorious stories out there. I was wondering if it did that about Fock spaces. I haven't gone into the math but from what I can tell a Fock space is a kind of Hilbert space that makes some important calculations a lot easier to do. See for instance https://math.stackexchange.com/questions/3819998/proof-that-fock-space-is-a-hilbert-space . So it is still true that the quantum field is a Hilbert space.

I'm more interested in arguments that the quantum field is itself physically real. It turns out that Faraday had a similar issue with trying to make the case that electric and magnetic fields were real. Kant was an opponent of this. He favored "the unmediated action at a distance of gravitation that would yield an epistemic ideal to which the alternative model of continuous action, with its hypothetical constructs, could not aspire. Easier far to treat such constructs as no more than mathematical devices, aids to the imagination, not to be taken in any way seriously in ontological terms." This is pretty much now how classically oriented physics talk about the quantum field.

Very interesting and useful. It has implications for the ontology known as "wave function realism" as well. That talks about the universe as being a 10^100 or so dimensional configuration space. That's off-putting enough in itself, and this makes it even worse..

Of course you always have to be careful with AI - it makes stuff up so needs confirmation. I asked one once about that and it said its defined task is to generate plausible responses. I said "Doesn't that make you a BS artist" and it said that they are similar but being an inanimate machine it does not have the capacity to have an intent to deceive, so it is not a BS artist. I consider that a BS answer that confirms my view, but didn't press it. Certainly making a distinction like that, however poorly, makes it somewhat like a philosopher.

You asked about sources I use for information theory. Actually this is becoming an almost mainstream approach for trying to unify gravity and quantum mechanics. Quantum information theory gives a way to model some of the events in quantum mechanics that are outside the traditional notion of what is physical - the "Bell's inequality effects." A starting point might be: https://www.semanticscholar.org/paper/Does-gravity-come-from-quantum-information-Qi/3be29be26eff01e1c2b182fca716180c11031ebd

A lot here but very interesting. It does remind of Hume's argument that we do not observe causation, just a sequence of events, but we impose it on to the experience, more or less conceptually.

Physics has no theory of how matter can warp space-time. But once it does that, the sense that something is pulling on us when we're walking up or down hill is actually caused by the surface of the Earth accelerating upward. Earth doesn't get any bigger when that happens because it has a property called "non-inertial" which I barely understand. All that now replaces the old force of gravity. But there are some ideas people are trying to work out saying that the quantum field is what is fundamental and that in itself actually creates space through informational effects. Maybe that will work out, maybe not.

Quantum theory changes everything. What seems to be a lump of matter is built up from something pretty non-material. There is no essential nature of matter because when you get close enough there are just probabilities of where things might be. That comes from waves in the quantum field that are not waves of force - but who knows what their nature is. The best theory now probably is the one that says they are waves of information. The probability of mass' position and momentum are just indicative measures of the waves and do not tell us everything about the waves. There is more going on in the quantum field than matter.

Because the nature of this field is still open for study, there is a real possibility that the best model will be that it is consciousness, or at least holds conscious potential in the same way it holds physical potential. And there are ways to quantify that mathematically in a way similar to how material potential is quantified. Bertrand Russell said that for all we know, the essential nature of matter and consciousness are the same. Now scientifically that might sort of hold, but it is more like they both arise from the same thing which in itself is neither. And there is a growing body of literature in physics that argues that quantum effects are necessary to explain brain processing, without even getting into the consciousness question.

The quantum field could be the prime mover!

I'm not sure about the universe as a whole, but physics is giving up on causation in the physical sense - a lot now is more like logical causation. In general relativity, a big mass, like the Earth, curves space, and that gives the illusion of a force of gravity, but there is no such force in physics anymore. And there is no mechanism for how the mass manages to curve space. Similarly in quantum mechanics, the Schrodinger wave equation does not let the electrons in an atom collapse into the protons in the nucleus, even though no force is created to oppose the electrical attraction pulling them in. How does an equation accomplish that? Sounds more like logical causation to me.

We use math to model the universe but all those models are open to further investigation, some of which is going on. For instance, the universe of Galileo was a three-dimensional Euclidean space. The universe of general relativity is a curvy space where even the curvature is changing all the time.

Both of those spaces use real numbers, but attempts to combine quantum mechanics and relativity have come up with alternatives, like a discrete space with very small but non-zero lumps of space time that cannot be subdivided. Another such attempt posits that the universe is on a curved 2-D space where information affects act mathematically to mimic the behavior of 3-D gravity inside the curve. Even our 3-D visual perception of the world is manufactured in the brain from 2-D input by specialized neural processes that have to be visually triggered in infancy. Evolution gave us a brain that presents a 3-D world to us because it is a good approximation that helps species' survival, not because it is real.

Some quantum theoretical interpretations posit that the universe is really google-dimensional, perhaps with even the number of dimensions changing, and 3-D space is a good approximation due to information effects.

Another alternative to real-valued dimensions comes from non-standard analysis - see (https://www.wikiwand.com/en/Nonstandard_analysis), which expands the reals to include infinitesimals, which are smaller than any real number but greater than zero, and their reciprocals, unbounded numbers, which are larger than any real but less than infinity = 1/0. See (https://www.researchgate.net/publication/330751668_Infinitesimal_and_Infinite_Numbers_as_an_Approach_to_Quantum_Mechanics).

Another QM interpretation holds that the quantum field is a Hilbert space, not just mathematically but actually, which would make the physical world part of the set-theory universe, reversing the question this thread raises. I personally find this non-appealing for a few reasons. One is that the 3-D Euclidean space of Galileo is also a Hilbert Space, but no one ever thought his universe was part of the set theory universe. Another is that you would then have to consider the reality of the set-theory universe, which would be an interesting thread in itself but is a lot to insert into physics.

In the end, how the universe is modeled mathematically is still up in the air. Inserting the mathematical universe into those physical models would not be very helpful.

Thanks. Fun to have found this.

True about the logic but natural language sentences do not have to be true or false. Of course "meaningless" is one alternative, but so are "mostly right but very misleading," "ambiguous," "changed the sense of a word in the middle of the argument," etc.

It can be problematic to apply formal logic to a natural-language statement. In formal logic you have rules of sentence formation, and these try to exclude contradictions. Natural language has informal, often ambiguous rules and definitions.

This a particular type of statement: the only argument for it is that it can't be false; the only argument against it is that it can't be true. But in natural language not every sentence is true or false.There are many other possibilities, including meaningless, as this thread suggests.

Indeed. It is famous for making things up. If you ask it about it, it says its task is to provide plausible responses. I asked if that makes it a con artist, and it quibbled about definitions.

Good info. Thx.

Maybe so. That's sort of a popularity contest. ChatGPT didn't give any data to support that either, but I meant conceptual support was not provided.

Some physicists are now saying that physics does not support the existence of the quantum world, which the classical physical world is made of. All it does, and all we need it to do, is predict our observations.

I expect that most people would agree that acting like the physical world is real would would work well in practice.

I personally take a skeptical viewpoint that there is no reason to accept any theories about the reality of anything, including the reality of the quantum world and everything built from it. Still there are appealing theories about quantum reality, all worth entertaining.

Here is some logical grounds for believing in the existence of the world from ChatGPT. — Corvus

Philosophy has become a classifying system for concepts and lines of reasoning, and all the branches the definitions and arguments could take. For instance there must be at least 20 types of panpsychism by now. New research, such as PhD dissertations, consists of following a line as far as it can go and then extending it in some way, probably by further splitting the track. Philosophy ends up having the same organizational structure as a book of chess openings.

ChatGPT has adopted the philosophical approach. Everything seems factual and devoid of evaluation, at least until the conclusion that "belief in the existence of the world is generally regarded as a foundational assumption of human cognition and inquiry, underlying our understanding of the natural world and our place within it," for which no support is provided.

You and Janus bring up a good point about "all models are wrong." Statisticians also objected to this and were offended. When I talk about Boxian Skepticism I usually say that "all models are subject to replacement or revision." The larger point is that right/wrong or true/false isn't the real issue. Or "How can we know for sure?" We can't. And "useful" goes beyond making predictions. A model that gives some kind of explanation of what is going on is more useful than one that just says "Here's the math." Also a model that goes somewhere is important - not a dead end - gives ideas of further possibilities to explore. Also thanks for the historical perspective.

Thank you. Seems like a great forum.

Thanks.

It is very confusing. Walking down a hill is easier than going up and it sure feels like a force pulling at you. When experts try to explain that they start getting into inertial and non-inertial reference frames. They say the apple is not falling off the tree but the Earth is accelerating towards it, but not getting bigger because it is doing that in curved spacetime. Huh? Anyway, a couple of links along those lines: https://www.physicsforums.com/threads/if-gravity-is-not-a-force-what-is-holding-us-down.1004751/#:~:text=It%20isn't%20easy%20to,exactly%20as%20a%20force%20would.

https://www.physicsforums.com/insights/understanding-general-relativity-view-gravity-earth/

Thanks for bringing this up. I wish I had a clearer picture odf it.

It used to be that forces obeyed certain laws but we didn't know why. But given that, the forces enforced those laws, pushing everything around according to their rules. But with quantum mechanics, the rules described by the wave equation cannot be enforced by forces. Physicists have proposed some ideas about how they do get enforced , but some of course regard that as philosophy, not physics. Still, those discussions do help create visions of what the world might be like.

It's similar with general relativity. There used to be a force of gravity. Now mass curves space and that produces what acts like a force, but explains the details better. How does mass manage to curve space? No body knows.

That's ultimately what science has to say about the even simpler question of how the universe manages to follow the laws that our models postulate.

There is no reason to believe in the existence of the world even if you are seeing it. First of all, there is no reason to believe in any scientific theory. The statistician George Box said "All models are wrong but some are useful." That takes science out of the dichotomy of true-false. A model is useful if it gives good explanations for many of our observations, and if it gives us some kind of picture of what could be producing what we see while opening up possible paths to still more useful models.

Quantum mechanics (QM) cannot explain everything, but it gives a lot of very good predictions. Unfortunately there is no way to understand it as traditionally physical, in the sense of particles controlled by forces through cause and effect. In the math a very distant object can be changed instantaneously by something happening here. That can't be due to forces because by the rest of physics, forces operate locally.

This makes it difficult to believe QM because no one can see how that can happen - but there are theories. One is that QM is just a bunch of formulas for prediction, but there is no real quantum world. That is a lot harder to accept now that we know that there is no traditionally physical universe. If the quantum world is not real, neither is our familiar physical world. This approach thus ends up in idealism - only the experienced observations are real. That is one alternative we might entertain but do not have to believe it - or anything else.

Other theories extend the physical world to include things we never thought were real, physical things, like for instance information. Another approach is that only the math is real - the physical world is part of the set-theoretcial universe and exists if sets do. None of these theories are particularly believable, but they are all possibilities worth exploring and some might be useful.

Secondly, the observed physical world is a structure created by our brains. People are not born being able to see in 3D - the incoming visual information is 2D. Sometime during infancy the brain creates neural structures that make this information appear to be 3D. This has to be done in the very unformed infant nervous system. Adults born blind cannot later after sight-restoring surgery learn to see in 3D - they see a very flat world. Seeing in 3D does not come from inference or reasoning of any sort. But evolution has found it useful for human survival and reproduction to produce our internal movies in 3D.

Plus 3D might not last as a physical framework either. Trying to cope with QM and relativity has produced non-3D models. A highly curved 2D surface seems to work reasonably well. But so does a universe existing in 10^400 or so dimensions which has some information structures that have good 3D approximations.

We don't have to believe in the existence of anything - doing so doesn't have much advantage - but exploring and entertaining the possibilities of competing theories - and developing new ones - can be useful to life.

The axioms of mathematics do have a subjective element. Math now all derives from set theory, so those are the axioms of math in general. When Paul Cohen published the final step of the proof of the undecidability of the continuum hypothesis, there was a lot of discussion about the need for new axioms. The general feeling was that you couldn't just add a yes or no axiom - any new axioms need to provide a more general picture of the set-theoretical universe, like what rules can be used to define new objects. Several promising axioms have been proposed, and over the last 50+ years a few of them have been found to be mathematically equivalent. Together they do give an expansive and exciting vision of this universe. However one other axiom has been proposed recently that gives different answers to some key questions. It is too new to know whether or not it will lead to an alternative but still expansive vision of the scope of the set-theoretical universe. If after enough time it does not, then the other axiom(s) will be widely taken as the right one(s). A lot of mathematicians involved feel that these will be true statements about the real sets. But clearly that is a subjective choice based on values about what axioms should do, and there is a cultural aspect to that.