Hi Emily,

Thank you for a well-written and thought-provoking essay. You present an excellent analysis of the problem of a purely predictive physics within the orthodox conceptual model of physics. Your examples (references [37, 38]) are very telling. Both cases "prove" that what nature does (or likely does) cannot be algorithmically decided in finite time. You offer two potential resolutions.

1) Physical reality may be limited to a subset of possibilities--I believe Tim Palmer explores this idea in his essay.

2) The universe has infinite time, and nature acts globally across time.

In my essay I explore a third possibility. Any proof is based on assumptions, and I suggest that the orthodox conceptual model of physics, on which the proofs in [37 and 38] are based, is lacking. Specifically, it rejects entropy and dissipation as fundamental properties of physics. As described in my essay, this is strictly a matter of interpretation of observations; this conclusion is not empirically based on observations. In thermodynamics, entropy is a fundamental measure of the relative stability of state, but in statistical mechanics, it is a measure of an observer's incomplete information and the observer's subjective description of the system's disorder.

With no fundamental definition of stability, it is impossible for an algorithm to select one possibility or another. The orthodox interpretations of physics have no irreducible "values" by which it can assign relative stabilities to different alternatives.

In my essay, I reference an essay ([13]) in which I define a measure of relative stabilities for alternative processes of dissipation. Referring back to your reference [37], this measure of stability would easily allow an algorithm (and nature herself) to decide which of different allowable emission spectra would (most likely) result as a quantum system transitions to a lower energy state. This third possibility interprets physical reality as objective, local, causal, and fully compatible with quantum observations, but with irreducibly random and irreversible transitions in state.

Harrison Crecraft

    Someone who reads to the end of my comment might rightfully conclude that an interpretation of physical reality that is objective, local, and causal violates Bell's theorem. I respond that the notions of locality and causality, described in my essay's reference [12], are more nuanced than in Bell's theorem, and that such an interpretation is fully compatible with Bell.

    Harrison

    Hi Prof.Emily Christine Adlam,

    Well written essay, after seeing your words .......after all, even if you are only interested in making predictions, you will most likely be able to make better predictions if you are using a theory which comes closer to the true laws of nature..................in the finishing part of the essay,

    I thought I should ask you to see the predictions of Dynamic Universe Model's that came true. For that you dont mind seeing my essay "A properly deciding, Computing and Predicting new theory's Philosophy" and give your learned comments please

    Best

    =snp.gupta

      Emily, when I read the title of your essay some days ago I thought it was about the usual "stuff". Nevertheless, I read your essay today and I am really impressed. I didn't keep my code to rate essays but in my opinion it is a 10.0.

      With kind regards, Sydney

        Hello Dr. Adlam,

        - I enjoyed your essay. What are your thoughts on (local and non-local) hidden variables? ("...there are still physicists who argue that the conclusion of Bell's theorem can be avoided, for example by the rejection of the statistical independence assumption[13], and if they're correct then perhaps we can actually have both locality and determinism..."

        - Do you ever have concerns about retro-causality? One could, after all, trace information and trajectories after something has happened (i.e. an electron was sent through a double slit and measured.)

        - As I'm sure you are you are aware, excavating the universe through means of experiments that are induced by artificial means (conditions that are pushed and are unlikely to be encountered in nature such as trying to probe the standard model for more elements to join the particle zoo) is in order to see the nature of unnatural phenomena (such things that are difficult to find in nature such as Higgs boson particles).

        - "...Now, it's useful to know that the halting problem is undecidable, but there's nothing particularly paradoxical about this, since after all the halting problem doesn't have to be decided in finite time in reality..." I don't know if you read Sabine Hossenfelder's essay "Math Matters". She argues that matters within realms of pure maths are not very helpful in practical areas of physics. Even though mathematics is extremely relevant to physics, physics is not mathematics. The latter is intuitive. Your above quote better succinctly describes pure maths and physics.

        - Conventionally related to [pure] maths, you gave an example of a problem which occurs in the physical universe that is applicable to physics and it is undecidable (using 'undecidable' in the traditional context of a mathematician).

        - I would also imagine that when you write about algorithmic programs terminating in some finite time, some time t would need to be somewhat reasonable.

        - "...thus it might seem natural to suppose that the universe should not be able to decide undecidable problems..." Even with infinite time it would not surprise me if one could prove that undecidable problems are still undecidable.

        - I'm currently reading "Quantum Mechanics and Global Determinism" that you wrote, too.

        - "...yet it seems that the universe must be able to determine the answer to this problem in finite time, in order to avoid producing examples of non-locality which violate the laws of nature..." Are there problems that could [theoretically] be solved with some infinite amount of time or would such a dilemma remain unsolvable? I suppose part of the definition of solvable implies "in some finite time"- am I correct? "...there would no longer be any paradox if it were able to solve problems which require infinite time to solve..." Indeed, I concur.

        - "...Well, first and foremost, physics will need to relax its emphasis on prediction. To be clear, this does not mean that we should stop demanding empirical evidence for out theories: if our aim is to understand reality, then our theorydevelopment and theory-selection need to be anchored in facts about reality, so I'm certainly not arguing that string theory or any of its similarly afflicted fellows should get off the hook for their failure to say anything empirically novel!..." Excellent point, worded wonderfully.

        -

        I will absolutely give you very high marks. I really enjoyed your essay, friend.

        Best regards,

        Dale Carl Gillman

          Dear Emily, thank you for a very creative, well-argued and provoking essay. Although quite speculative, the ideas you introduce are remarkable and perhaps could help to oppose some form of scientific reductionism and take into serious account the possibility of more "holisitic" (in the sense of inputting the whole history of the Universe), as you say: "Insisting that all theories should take

          a predictive form from the start places an unnecessary and unjustified constraint on the space of possible theories, and by removing that constraint we will probably be able to do better physics".

          I also highly appreciated your general challenge, expecially when you write: "All of this amounts to a fundamental failure to distinguish between the laws of nature that scientists write down and the laws of nature that actually govern reality".

          I have then some more to-the-point comments.

          When you assert:

          "Why do we assume that the universe can only take information about the past into account when deciding on measurement outcomes? Well, there are obvious social and historic reasons." Ithink this statement is quite strong. I understand that your aim here is to redefine the scope of science, but in my opinion science has been conceived, or invented if you want, to explain/understand and predict. You would like to relax the latter feature. Yet, in my opinion, there is more than a mere social-histioical reasons to this. It seems that the past leaves traces and that the future does not, for this asymmetry of "memories" (see e.g., https://arxiv.org/abs/2003.06687). This reason seems to be the actual cause of the predictive character of laws to me. We can surely question whether this asymmetry is fundamental in mature or if it is a fundamental limit of humans, but my point is that is not an arbitrary social construct.

          About quantum mechanics, you write that the mechanism for probabilistic predictions is usually considered to be "objective chance". I don't think this is the case in the community of quantum foundations, for the propensity interpretation has hardly any supporters these days. On this note, I don't understand the following statement: "However the idea of quantum probabilities as propensities should raise red flags, because quantum systems don't have psychological states and therefore they can't actually have inclinations." What has this to do with propensities? The fact thet they are called 'propensities' or 'tendencies' should not mislead us towards any psychological state. Propensities are supposed to be objective properties, of the same kind of fragility. You need not to through on the ground a vase of fine crystal to know that (due to it composition and thus to its property of pragility) that there will be a high chance for it to break.

          I wish you the best of luck for the contest!

          Cheers,

          Flavio

            Thank you very much for your incisive comments!

            With regard to the arrow of time - this is a good point, and I certainly agree that the arrow of time does need to be explained. However, I don't agree that `predictive' (i.e. temporally directed) laws of nature are the only possible explanation for this phenomenon - it could, for example, arise from global time-symmetric laws together with some sort of symmetry breaking. Thus the existence of the arrow of time is not enough to show that the laws of nature must be temporally directed - we should at least consider other possibilities, such as global laws.

            I agree that within quantum foundations specifically it is less common to invoke objective chance when describing quantum probabilities, because many people in quantum foundations favour interpretations wherein the quantum probabilities can be understood as epistemic. Among physicists more generally, however, it is still very common to say that quantum mechanics is 'inherently probabilistic' and this usually seems to be understood as referring to propensity-like probabilities.

            I appreciate that proponents of the `propensity' view don't actually intend to ascribe psychological states to quantum systems. My concern, however, is that using metaphorical language like 'propensity' and 'inclination' they are implicitly invoking psychological ideas which make the propensity view sound better founded than it really is. Once you take away all the psychological language it's much harder to understand what sort of property a propensity is - it seems to be an intrinsically counterfactual property, which makes it very different to fragility, which is a physical property relating to ta substance's chemical/physical constitution. My contention is that once you take away the unhelpful 'propensity' metaphor and consider what objective chance actually achieves, it is clear that objective chance is really a collective property of a set of systems involving coordination across space and time.

            Thank you for your thoughts!

            I'm impressed that you counted the number of words in that footnote! Which word in particular do you object to?

            Thank you for your comments! Some interesting things to think about there.

            That's interesting - I certainly agree that we have been too quick to jump to the conclusion that quantum mechanics is inherent probabilistic, but how does your model deal with the Colbeck-Renner theorem and similar results?

            Thank you! Yes, I certainly agree that it's important to recognise that our perspective on the world is limited and thus the laws of nature we are able to write down are not necessarily identical to the `true' laws of nature (whatever that means!)

            Thank you for your comments! Your third way out of the problem sounds very interesting and I'll read your essay as soon as possible.

            Thank you very much! I'll have a look at your essay as soon as possible.

            Thank you very much for your comments!

            Yes indeed, I've thought a lot about retrocausality. Basically, I think there are two different `types' of retrocausality - either you can have both a forward and backward arrow of time, or you can just have global laws (e.g. optimizing some constraint over the whole of history) which implies that what happens at one moment affects what happens at all other moments, past and future. I agree that the first type leads to contradictions of the type you mention, but I think the second type avoids that problem because the global equations will necessarily be solved in a consistent way.

            Yes, I enjoyed Dr Hossenfelder's essay very much. It's a very interesting question to determine exactly which problems of pure maths translate over into physical reality - I'm sure there are many applications which we are yet to discover!

            Hmmm, interesting - my intuition is that undecidable problems would become decidable if you allow yourself infinite time to solve them, but I'm not aware of any results one way or another on this question!

            Thank you, this sounds very interesting? I presume it's discussed in your essay? I will take a look!

            7 days later

            Emily I loved your essay. To me it is "on stream". Probably because it describes what I did in developing the Successful Self Creation theory described in my essay. I got rid of all of the laws, rules, impossibles, etc. of current physics, started from a very different beginning and developed a theory with causes, retro causes and global causes in every SSC progression. In doing so I was able to derive a complete, mathematically consistent, explanation of the creation process that provides measurements that match the "generally accepted as true" measurements of the visible universe as well as the Planck measurements and the measurements of the major components solar systems, galaxies, etc.. In my derivation, I did not assume the laws and constants of physics were wrong - they just were not in existence before the beginning and are not in effect everywhere, all of the time and never change. The are created by the process as a component of the observed results. If you want to see your ideas put into actions and results read my paper. "Clarification of Physics: A Derivation of a Complete, Computable, Predictive Model of "Our" Multiverse". While the paper may seem simplistic, the differences from current theories are profound. For example the process makes its own mathematics as a component of the processing, gets rid of infinities and zero which allows for a complete mathematical explanation. I would appreciate your comments. John

              9 days later

              Emily I have "revised" my essay. In that revision I develop in more detail how the SSC processing produces its own mathematics and algorithms. The system in its encapsulation step also solves its own "halting problem". It instills it's own limits and boundaries. It solves the problems we are trying to impose on it. It creates its own temporal progression. In the revision I also extend the SSC fundamentals and their role in the other disciplines of science, philosophy, mathematics and religion. If you have already read the first edition of my essay, I suggest you read the revision and base your comments on it. John

              8 days later

              Dear Emily Adlam,

              You might be surprised: My essay tries putting the pre into mandatory physics. That's why I carefully read your essay. If I understand you correctly, you are hoping that accepting the weird retrocausal theory may yield better predictions by removing a constraint. Is there any evidence?

              I suggest calculating for convenience as usual, as if Einstein was correct and the now that does distinct between pre and after, past and future was an illusion. While I like backpropagation NNs, my point is that the map, the theory including the laws of nature is not the territory, not the reality. My stance has unwelcome consequences. Do you feel in position to defend?

              Regards,

              Eckard Blumschein

                Dear Emily,

                I think your essay digs around some questions that have become crucial in physics this century, and can be seen as part of a self-searching process that science is now engaged in. To some, it's an identity crisis, but however one takes it, it's very helpful to shine a searchlight on these questions, as you do.

                I also tend to take an overview kind of position, standing further back, as you do - to me two of the strands you mention need to go hand in hand: conceptual understanding, and the empirical side, mathematical theory/experiment. I agree that there's more to conceptual understanding that just a reverse form of prediction, though it's a good point nonetheless (you mention in a footnote that identifying emergence is another way we sometimes reach understanding).

                To me, with a jigsaw for a loose analogy, theory and experiment tells us how the pieces fit together, but conceptual understanding - seeing the picture - is also essential. They need to work together, each informing the other.

                I think the reason we're having to question our aims now is that one of these strands got left behind during the 20th century - theory/experiment got ahead. So the conceptual side needs to catch up, and we need to interpret the mathematical theory that we have.

                The main point in my essay is that to interpret QM, missing concepts must be found. Several things suggest missing concepts, including the lack of consensus on how to interpret the theory. But also the physics itself - apparently fundamental unpredictability, non-locality, superposition. If there are missing concepts that encompass these, we'll need to find them.

                Anyway, congratulations on another good essay - I hope you'll read mine, which is here. As well as looking at the overview and the different strands, it summarises an entirely new interpretation for QM, which anyone interested in quantum foundations might find interesting. A documentary was made partly about the interpretation last year, with some well-known physicists discussing it. I'd very much like to hear any thoughts you might have on my essay.

                Thank you, best regards,

                Jonathan