"I doubt that the question "Which of Our Basic Physical Assumptions are Wrong?" can be really answered in a cordial discussion among colleagues."

- what an extraordinary statement. I hope to never be in an institute where this is true. My own personal colleagues are able to behave in a collegial fashion. It is the hallmark of civilised discussion that you don't have to be rude to your opponent if you disagree with her/him.

"I see what you are calling bottom up causation the principle of superposition of influences. If you could really question it, then it then I was surprised. I will read you essay again. Maybe I overlooked something." Superposition is a linear interaction. Most real system in the universe are not linear. Yes they are based in linear interactions at the bottom level, where superposition holds, but these are put together in structures and complex interaction networks that result in non-linear behaviour at the higher level. These structures then act down in a non-linear ways on their component entities to allow them also to behave in a non-linear way. Example: state vector preparation (a non-unitary process). Example: superconductivity, where the lower level entities (Cooper pairs) only exist because of the context provided by specific crystal structure.

Many other examples are given in my more technical article on which this essay is based, see here .

George Ellis

Just for information, re the previous interchange: this is the proposal for the Nature of physical reality I make in the technical article I referred to:

1. Combinatorial structure: Physical reality is made of linearly behaving components combined in non-linear ways.

2. Emergence: Higher level behaviour emerges from this lower level structure.

3. Contextuality: The way the lower level elements behaves depends on the context in which they are imbedded.

4. Quantum Foundations: Quantum theory is the universal foundation of what

happens, through applying locally to the lower level (very small scale) entities at all times and places.

5. Quantum limitations: The essential linearity of quantum theory cannot be assumed to necessarily hold at higher (larger scale) levels: it will be true only if it can be shown to emerge from the specific combination of lower level elements.

"wherever equivalence classes of entities play a key role, ... this is an indication that top-down causation is at play."

The real numbers are defined as equivalence classes. OK, perhaps "functional" equivalence classes are meant, and I do not know what functional means in this context.

Are standing waves a convincing example for top-down causation? As an EE, I would like to distinguish between waves that are really bouncing back and forth in a cavity and the abstract mathematical model which endlessly extends within the abstract fictitious time scale from minus infinity to plus infinity and ignores the trifle that a real "standing" wave always has a begin and an end, cf. my Fig. 1.

Let me go one searching for something truly basic that elucidates at least one out of the various enigmas and paradoxes I listed at the beginning of my essay.

Eckard

Dear Johnathan Kerr,

In my essay thread "What basic physical assumptions are wrong?" Georgina Parry, there is a high resolution version of diagram 1. which shows an explanatory framework for physics that addresses the problem you have just mentioned.

It isn't a block universe model but there is sequential iteration of the material aspect according to the existing relations and various constraints of physics and biology. Eg.conservation of energy, Pauli exclusion principle, minimisation of potential energy,inverse square law, relationships of volume and surface area, effects of concentration gradients, natural selection. The visible universe (including that which is visible using technology) is not that material one but a fabrication generated from received data, that was emitted or reflected from the material universe. This structure allows the universe of atoms and material things, going about their actions simultaneously, to coexist without contradiction with Einsteinian relativity.

It is an unusual structure because observer fabrications must exist wholly within the material reality even though they are different from it and show something different from what exists independently and simultaneously.For analogy: As Terry Pratchett's Disc World and Tolkien's Middle Earth exist within our world but are at the same time not our world.

The time that is shown by observation of the distant clock is different from the number or hand position that -is on the clock- independently, and the objects that are seen are also amalgamations of data formed by the observer not independent things-overcoming many paradoxes.

This is a matter of preference. You cite the incorrect Dirac's phrase. I cite the modern correction by P.W. Anderson.

The Science paper does not confound reductionism with causality and shows how the emergence of new properties at higher levels is compatible with the ordinary bottom-up causation of physics. Murray Gell-Mann, another Nobel laureate who is now working in complexity at SFI, has an entire book devoted to such issues. The physiology of the heart is also compatible with ordinary bottom-up causation.

Anyone reading this amusing essay should look at Weinberg's proof of Boltzmann's H-theorem (p.150 of volume 1 of "The Quantum Theory of Fields"). This modern proof of entropy increase is formulated in the language of quantum field theory and avoids approximations, such as the Born approximation or time-symmetry invariance, which are used in ordinary statistical physics proofs. Cosmology is unneeded in the proof of the H-theorem.

You name two cosmologists. Their work is incorrect. One of them gave a talk in Santa Cruz promoting the idea that cosmology is the cause of the second law of thermodynamics. One expert at the audience said:

"Finally, the magnitude of the entropy of the universe as a function of time is a very interesting problem for cosmology, but to suggest that a law of physics depends on it is sheer nonsense. Xxxxxxx's statement that the second law owes its existence to cosmology is one of the [dumbest] remarks I heard in any of our physics colloquia, apart from [Rosenblum & Kuttner]'s earlier remarks about consciousness in quantum mechanics. I am astounded that physicists in the audience always listen politely to such nonsense. Afterwards, I had dinner with some graduate students who readily understood my objections, but Xxxxxxx remained adamant."

You write "It is conceivable this review could lead me to change my opinion". My goal was to expose some elementary facts ignored in your amusing essay.

1: "Murray Gell-Mann, another Nobel laureate who is now working in complexity at SFI, has an entire book devoted to such issues." That book is about adaptive selection, which is a form of top-down causation, as has been very clearly demonstrated in many writings since the seminal paper on the topic by Donald Campbell; see for example the book The Re-emergence of Emergence edited by Clayton and Davies.

2. "The physiology of the heart is also compatible with ordinary bottom-up causation." This dogmatic statement is simply wrong. Denis Noble is a world authority on the physiology of the heart, and there is no reason what ver to believe you know more about it than he does.

3. "Cosmology is unneeded in the proof of the H-theorem." Indeed. And the result is a theorem which does not resolve the problem of the arrow of time because it continues to hold when you reverse the direction of time. Extraordinary that you call time-symmetry invariance an approximation, when it is at the heart of all fundamental interactions except the weak interaction. Are you trying to say that the cause of the arrow of time is the very small weak time asymmetry of the weak interaction? If so please explain how this works. No one who has looked at it seriously believes this.

4. "You name two cosmologists. Their work is incorrect." I am totally unimpressed by someone hiding behind a cloak of anonymity making such a statement. What standing do you have to dismiss two of the deepest thinkers in cosmology? You then quote some unnamed other person who is supposed to an expert on the subject. The tone of the response shows they, like you, are simply unable to engage with the core issue: it is not that the second law owes its existence to cosmology, it is that the statistical derivation of the second law predicts equally that entropy will increase both to the past and the future because it applies whichever arrow of time you choose. The same applies to any derivation from quantum field theory, unless it claims to derive the arrow of time for all physics from the weak interaction, which is totally implausible. If they and you can't even admit the problem exists, then you have nothing useful to say on the arrow of time.

5. I note with interest how you fail to respond in any way to my remarks on the issue of superconductivity as discussed in Laughlin's Nobel lecture. It shows conclusively your sneering comments are simply wrong, and I do not believe for one minute that you understand it better than he does. No wonder you ignore it.

By the way as regards the pseudonym you hide behind ("There is nothing new under the sun"): this is of course also incorrect. Amongst the thousands of examples I could cite, one will do: digital computers and the internet.

    For those of you who are interested in the relation of this topic to the brain, Karl Friston's article A theory of cortical responses is excellent. He emphasizes the key role of hierarchical structuring in the brain. His "forward connections" are what I call bottom up, and his "backward connections" are what I call top-down (the difference in nomenclature is obviously immaterial). He makes quite clear that a mix of bottom up and top down causation is key as to how the brain works; backward connection mediate contextual effects and coordinate processing channels.

    This is how the theme works out in a genuinely complex case. It is obviously compatible with the underlying physics, because it does indeed work. As in the case of digital computers, which can run any algorithm whatever, in the case of the brain the underlying physics enables us to think, but does not constrain what we are able to think about.

    George

      Ok I have looked at the Weinberg derivation (pages 150-151 in his book). I agree it's good to have a derivation that depends only on unitarity. Unitary transformations however are time reversible. There is therefore nothing in the dynamics that can choose one time direction as against the other as far as any dynamical development is concerned, just as there is no intrinsic difference between the particles alpha and beta.

      Consequently just as in the case of the Boltzmann derivation of the H-theorem, the H-Theorem (3.6.20) will hold for both directions of time (just reverse the direction of time and relabel alpha to beta: the derivation goes through as before). This is the point which is explained very clearly by Penrose in his various books as regards Boltzmann's derivation. Weinberg's derivation of the H-theorem does not determine a preferred direction of time from the underlying unitary dynamics. It can't do so, as there is no preferred direction of time in that dynamic.

      " As in the case of digital computers, which can run any algorithm whatever, in the case of the brain the underlying physics enables us to think, but does not constrain what we are able to think about."

      Right on, George. Androids may dream of electric sheep, but only a human brain can dream of an android dreaming of electric sheep.

      The capacity for infinite regress cannot be programmed into a finite state machine.

      Tom

      The point of the above is that it is impossible to derive the arrow of time - one of the most important aspects of macro physics and biology - from microphysics alone. Both statistical physics and quantum field theory give you a beautiful H-theorem: and the derivation applies equally in both directions of time (this applies for example to Weinberg's derivation of the H-theorem: see my last comment). Supposing you break this symmetry somehow by random fluctuations: you have no guarantee the direction of time will be the same everywhere. We do not see opposing arrows of time in the real universe. Bottom up causation alone is incapable of giving an explanation of one of the most important features of everyday physics.

      Consequently, as pointed out by Wheeler, Feynman, Sciama, Davies, Zeh, Carroll, Penrose, and many others, one needs some global boundary condition to determine a consistent arrow of time in local physics:a top-down effect from the cosmological scale to everyday scales. This is what the Santa Cruz "experts" have not understood, even though the issue has been known since the time of Boltzmann and Loschmidt.

      This global coordination is plausibly provided by a macro-scale low entropy condition of the early universe, see the writings of Carroll (From Eternity to Here: The Quest for the Ultimate Theory of Time) and Penrose (Cycles of Time). For readers who have not encountered this debate, a useful summary by Sean Carroll is here ; and

      here he gives extensive quotes from Feynman on the issue. For my own summary of this and other top-down effects in cosmology, see here .

      George

      Dear George,

      these are just some things, pertaining to your last post, that I think are worth considering, not necessarily requiring an answer now. What is the real universe, in your opinion? Impossible is a very strong word, are you sure?

      There is a high resolution, horizontal version of diagram 1 in my essay thread.A reality interface can be a 'simple' light sensitive material such as cine film which changes in chemical structure when exposed. It does not have to be the sensory system of a sentient organism or a complex artificial detection device. Respectfully, Georgina

      Hi George,

      Indeed, I do appreciate the Martinez-Moya reference.

      I have thought for some time that brain science is the next great frontier of knowledge, because my wildest conjecture is that the brainscape perfectly mirrors an isolated cosmoscape in a simply connected network. Not to be too sci-fi on the subject -- as you say, " ... as pointed out by Wheeler, Feynman, Sciama, Davies, Zeh, Carroll, Penrose, and many others, one needs some global boundary condition to determine a consistent arrow of time in local physics:a top-down effect from the cosmological scale to everyday scales." (In fact, that's what my essay in this competition is about.)

      The introduction of multi-level causation to biological evolution, multi-scale variety (Bar-Yam) to all systems, IGUS (Gell-Mann & Hartle) to information theory, local arrows of time to cosmology (Ellis, et al) ... and more ... have persuaded me that a continuum of complex multi-scale connections reflect a deep truth of how the universe works.

      Martinez and Moya allow, "By highlighting the mutual co-determination between levels of organization in the process of natural selection we have recovered and articulated a multilevel perspective that is absent from previous discussions." And they quote Hitchcock 2003, "The goal of a philosophical account of causation should not be to capture the causal relation, but rather to capture the many ways in which the events of the world can be bound together."

      Bar-Yam puts it this way: "In considering the requirements of multi-scale variety more generally, we can state that for a system to be effective, it must be able to coordinate the right number of components to serve each task, while allowing the independence of other sets of components to perform their respective tasks without binding the actions of one such set to another." [Y. Bar-Yam, "Multiscale Variety in Complex Systems." Complexity vol 9, no 4, pp 37-45 2004]. In other words, distributed control -- lateral information -- increases variety. Increased variety increases the coordination strength of the network.

      George, may your tribe increase. :-)

      Best,

      Tom

      Dear Prof Ellis

      I enjoyed reading your essay and was prompted to also read your other papers that you cite. In one of those you mention Wheeler's delayed choice experiment as "a case of top down causation from the apparatus to the very nature of the particle/wave at the time it passed through the slits." In this instance, top down causation sounds a lot like retro-causation through the role of future boundary conditions (as modeling measurement processes) in selecting what actually comes about.

      In this regard, I think you would find interesting Couder and Fort's bouncing droplet quantum analogues of single-particle diffraction and interference (refs [18],[21},[23] in my essay). Retro-causality also plays a second role in this system: the analogue of de Broglie's pilot wave is a standing wave (not a phase wave), in other words the particle is the source of a semi-retarded plus semi-advanced radiation field.

      I have some ideas on the classical to quantum cut that I tried to explain in my essay, again related to retro-causality.

      cheers

      Andrew

        Dear Andrew

        your paper is very interesting, and I like its seriousness and originality.

        I agree on the possibility of retro-causality: please see this paper for a view that is a bit similar to yours in that regard. I also like the multi-scales in your model, which accords with what I am trying to do here. However of course quantum theory has to do much more than just model an electron: it will be very interesting to see how you take it further.

        Best wishes

        George Ellis

        Hi Georgina

        well the word "impossible" here relates to the relation between two theories that are supposed to describe the real universe on different scales.

        If you have a theory T1 that describes it on a small scale L1, you can in principle coarse-grain to get a theory T2 that applies on a larger scale L2. This is what happens for example with the kinetic theory of gases. Now if the theory T1 is subject to a symmetry S1, for example time-reversal invariance, then unless the averaging procedure explicitly breaks that symmetry, for example with an averaging procedure that changes with time, the theory T2 must necessarily exhibit the same symmetry. That is what underlies the discussion above: we believe that fundamental physics is time symmetric (more accurately: it has a PCT symmetry, as Sean Carroll explains), so any derived coarse grained theory must also be time symmetric. There is no option about this: that logic is where the word "impossible" comes from.

        However the time asymmetry can come not from the dynamic equations of the theory but from the boundary conditions. That is what Wheeler, Feynmann, and many others have explored. Then it is a top-down effect from the context (the environment) to the solutions.

        I agree completely about the reality interface. It can also be a plant leaf (chlorophyll acts the way you describe). Indeed any photo detector will do, such as a CCD in a camera, where a free electron is emitted at a detection event. Indeed it is free electron emission that underlies also the detection events you mention. You might find interesting my discussion of detectors in sections 6.2.2 and 6.2.3 of this paper (which also discusses the averaging procedure I mentioned above in some detail).

        George