Hi Don,
Thanks, you found the way to my essay.
What does moon mean, if it would not be observable at all? Would you still claim it exists?
Luca
Hi Don,
Thanks, you found the way to my essay.
What does moon mean, if it would not be observable at all? Would you still claim it exists?
Luca
Luca, even if not observable a prediction could be made of the moon's material existence from observed tidal forces. It does not need to be seen to have gravitational effect on the oceans.
If it has gravitational effects on the oceans it is observable. But here lies the core of the realism positivism debate. If only coarse grained effects are operational accessible, does the moon have other hidden properties?
Luca,
I do think you are making an important point early on about the different way circumstances can be interpreted. Also you make good points about what can't be observed and that measurements are relative and not absolute. Mentioning the complication that implies.
If one is only interested in flower consumption (measurement protocol) and correlated weight, for meat production then wool colour is irrelevant. The numbers matter.
Being realistic a question is, whether to increase meat production low weight sheep should be eliminated or black flowers. Should the purchaser buy only white sheep or is the colour irrelevant. Should the farm technician feed only white flowers or is their colour irrelevant.
The measurements can now be used together with a hypothesis to make a decision about what is happening. 1, Is sheep genetics, linked to wool colour, (predetermined) causal, or 2, is diet and behaviour (unfolding over the process/(measurement through diet in your analogy) causal. It isn't a matter of opinion. Hypothesis: weight will change if diet is altered to the opposite choice. Method: Remove all the ones that have been found to be light weight (by diet choice). Then feed the heavies black flowers and the separated light weights white flowers.
The classical physics realist notion is more like the first case,"We have seen in the classical sheep that only the difference of the amounts of flowers is sensitive to the color of the sheep" Luca. The quantum mechanical more like the second. "The sheep flower system evolves..." Luca. Though because of the connection made between colour of wool and weight it would be necessary for the sheep to be able to change colour when their weight alters. Which is why I made the suggestion of canaries with the potential to change colour, Flamingos would work too for the same reason.
Typo p6 "black whole",
You do talk about how what is considered fundamental can change as conceptual capabilities grow. A good point. Quantum physics provides a good example of something considered by many to be fundamental but being a relatively recent development in physics.
I think the question of does the moon have other hidden properties is a bit like does the tree that falls when no one is listening make a sound? It is a question of whether independent qualities of something or some happening are being considered, beables, or attributes or associated facts gleaned from the realtionship of the observer with sources of information, including effects on the environment, measurables.
Are there vibrations from meteor impacts on the moon surface? I'd say yes and that could be detected with sensors on the surface. Impact craters tell us there are impacts, so the vibration of the impacts is a realistic assumption that can be made into measurables with the appropriate equipment and mission to place it on the surface. I'd say other physics is happening to the beables on the moon, such as due to solar radiation, that could also be investigated with apparatus allowing collection of measurables.
Like hide and seek, whether something is hidden depends on whether you are looking for it, firstly. As the word hidden is associated with seeking. Secondly do we have the capability to conceptualize its existence, and initiate seeking? There are differences between potential knowns, 'hidden' yet find-able, or potentially find-able with development of the technology, or the desire to seek, not find-able because it is unknown and unconsidered, so there is no search and not find-able because it isn't there to be found. Like the realist presumed hidden cause of a result, when that result is only actualized by the measurement process.
Hi Prof Luca Valeri
wonderful OP...."As a realist I imagine the world consisting of fundamental things with properties, that are independent of whether they are observed or not. In this essay I try to defend a positivist view, where properties only exist relative to an observer. The observer must not be a human being. I will explore a toy model, where a sheep is in a box and I want to find out what color the sheep has by giving the sheep different flowers to eat."....Nice work ...
I hope you will not mind that I am not following main stream physics...
By the way...Here in my essay energy to mass conversion is proposed................ yours is very nice essay best wishes .... I highly appreciate hope your essay ....You may please spend some of the valuable time on Dynamic Universe Model also and give your some of the valuable & esteemed guidance
Some of the Main foundational points of Dynamic Universe Model :
-No Isotropy
-No Homogeneity
-No Space-time continuum
-Non-uniform density of matter, universe is lumpy
-No singularities
-No collisions between bodies
-No blackholes
-No warm holes
-No Bigbang
-No repulsion between distant Galaxies
-Non-empty Universe
-No imaginary or negative time axis
-No imaginary X, Y, Z axes
-No differential and Integral Equations mathematically
-No General Relativity and Model does not reduce to GR on any condition
-No Creation of matter like Bigbang or steady-state models
-No many mini Bigbangs
-No Missing Mass / Dark matter
-No Dark energy
-No Bigbang generated CMB detected
-No Multi-verses
Here:
-Accelerating Expanding universe with 33% Blue shifted Galaxies
-Newton's Gravitation law works everywhere in the same way
-All bodies dynamically moving
-All bodies move in dynamic Equilibrium
-Closed universe model no light or bodies will go away from universe
-Single Universe no baby universes
-Time is linear as observed on earth, moving forward only
-Independent x,y,z coordinate axes and Time axis no interdependencies between axes..
-UGF (Universal Gravitational Force) calculated on every point-mass
-Tensors (Linear) used for giving UNIQUE solutions for each time step
-Uses everyday physics as achievable by engineering
-21000 linear equations are used in an Excel sheet
-Computerized calculations uses 16 decimal digit accuracy
-Data mining and data warehousing techniques are used for data extraction from large amounts of data.
- Many predictions of Dynamic Universe Model came true....Have a look at
http://vaksdynamicuniversemodel.blogspot.in/p/blog-page_15.html
I request you to please have a look at my essay also, and give some of your esteemed criticism for your information........
Dynamic Universe Model says that the energy in the form of electromagnetic radiation passing grazingly near any gravitating mass changes its in frequency and finally will convert into neutrinos (mass). We all know that there is no experiment or quest in this direction. Energy conversion happens from mass to energy with the famous E=mC2, the other side of this conversion was not thought off. This is a new fundamental prediction by Dynamic Universe Model, a foundational quest in the area of Astrophysics and Cosmology.
In accordance with Dynamic Universe Model frequency shift happens on both the sides of spectrum when any electromagnetic radiation passes grazingly near gravitating mass. With this new verification, we will open a new frontier that will unlock a way for formation of the basis for continual Nucleosynthesis (continuous formation of elements) in our Universe. Amount of frequency shift will depend on relative velocity difference. All the papers of author can be downloaded from "http://vaksdynamicuniversemodel.blogspot.in/ "
I request you to please post your reply in my essay also, so that I can get an intimation that you replied
Best
=snp
Hi snp,
I won't read your essay, because you did not read mine but just post in every blog the same comment with a citation of the abstract. Seems your are not interested in a discussion.
Also I don't belief you will ever read this reply.
Luca
Luca,
Interesting, fundamental and nicely written. But who let the sheep out of the box and into the field!?
I confess at times, (and as it's getting late and I've been on the Bollinger), counting your sheep I often lost touch, as Georgina seemed to. I think I finally grasped it all. I still think Bohr's and the positive formulation flawed. I agree NO retro causality, but I then prefer Bells choice to the Lamb (or mutton?); A different starter, then classical beables with scattered fermions, finished with an Eton mess.
You didn't claim you understood my essay so I'll explain. We know polarizers change polarization. So yes, ONE quality is retained, which is 'which pole? N/S (A,B) but the observer dictates the rest, including by field angle rotation (as Zielingers work confirms). Pairs then have Maxwell's 'curl' AND (orthogonally) linear momenta, changing inversely by cos latitude, so by rotational velocity (right the way through)! imparted from the field fermions by absorption /emission. A,B can then 'flip' polarity. Now follow that carefully through, including the 3 rotational axes and two orthogonal measurement angles then CosLat again at the photomultiplier. You'll find all Beables and no non-locality needed to reproduce the interpretational mess at the end.
I use logic & geometry not algebra or maths (despite top score of the Wigner essays!) so the ontological mechanism does need a formulation check. You seem good at that. Any chance of help? Declan Traill's short essay gives the computer code & Cos^2 plot.
So do properties ONLY exist relatively to observers? I suggest Yes & No. All do but many not determinable as changed by observation.
Nice description, argument and writing generally. Well done. Expect a score boost. I hope you have time to study mine in more detail and discuss.
Very best
Peter
Luca,
This is a well-written essay that would be a nice chapter in an intro to quantum book. The "fundamental " for this essay seems to be quantum mechanics. Only problem with this essay is a style and editing choice, I feel the theme of this essay is buried. "The rules of quantum mechanics are the rules of the universe and now I will show you an example of why that is possible." Or similar statement would be a nice place to start and end this essay. The wonderful thing about fundamental is that it is what it is and a statement like I suggested is as good as any.
Hope you do well,
Jeff Schmitz
Dear Peter,
Thanks for reading and replying. I certainly will read again more carefully your essay, as I also want to apply my interpretation to EPR.
As you ask: "So do properties ONLY exist relatively to observers?" Well I don't know.
The great simplicity of the known fundamental laws suggests that nature is fundamentally simple, mathematical.
As religious person and as a atheist I find that not satisfying. So I came to belief that the math is brought in by the relation of things, by their interactions. By simple operations of putting one ruler after the other and counting how many I need to come from one point to another.
In my essay I discuss what the consequences could be if properties are defined by such simple operations and under what condition such operations can successfully define these properties. I find that the consequences of such a thinking could be quiet fantastic. Without trying a bit to hard to find the underlying reality, that explains these quantum phenomena by introducing any ad hoc mechanism that does the job.
You'll hear soon from me.
Luca
Dear Jeff,
Thanks for the "well written". To write in English is very hard for me.
For the editing choice you're certainly right. The essay is surely very dense and touches to many topics.
Now after reading also some other essays I found that I expect the reader (that does not know me) to trust me to much and to follow me in my thoughts. That is to much to expect.
Also I trust the reader to make the right connections to debates in the history of science or in the discussions of quantum mechanics. Next time I surely will guide the reader much more and not let him alone in the jungle of connections.
Best regards,
Luca
I want to make some things clear in my essay, that apparently have not been clear enough.
The sheep that has only the properties white or black stands for a particle having the properties up or down. Or having the property of being somewhere in space. The use of the sheep is just to be able to imagine something as real as possible. The sheep has not even the properties of being in space. And I even don't know how to put the sheep in a box, if it has no properties of being in space. But this is exactly the situation we have in experiencing the outside world. We only know things from this world through interaction with the outside world.
The measurement system is modelled as a field of flowers over the colors. It is meant to be a mathematical field over the colors, as the electro magnetic potentials are fields over space and time. That the words 'field of flowers' has a real meaning is just a nice - although confusing - coincidence.
In the essay I explore, what can be known about the properties of the sheep, given the laws of interaction. And postulate in positivist faction (and I would say in accordance to the Copenhagen view), that only properties relative to the measurement system are real. I also explore, what could be the epistemological consequences of such a view.
However: Contrary to Copenhagen the measurement system is treated as quantum system.
Contrary to many worlds and Rovelli's relational view, this relative view is objective.
Objectivity is achieved not as in the decoherence view by losing the phase information in the environment, but on the contrary, by postulating that the measurement/definition of the properties is only well defined if it the object measurement system is separable from the environment and hence the evolution on that subsystem is unitary.
These are the main ideas concerning the measurement problem in my essay. I hope these explanations facilitates the reading.
Dear Luca,
Thankfully I was drawn to your essay by the comments that you made to others. However, I found your deep essay to be heavy-going with the sheep; possibly because I believe that quantum-analogies do not help. Thus, as a true local realist, I prefer to deal with the quantum settings themselves. Hence my essay: More realistic fundamentals: quantum theory from one premiss
[nb: contrary to the view of some, "premiss" is a valid spelling in logic.]
Thus I'm hoping that my essay might have some appeal for you, given your comment to Ian Durham: "What a nice idea to use Bell's theory of beables to discuss, what is fundamental. Bell's view of beables - I believe - is how most of us think about how the universe looks like."
For on this we agree: "The EPR reality criteria has to be given up."
Also, I believe Bell used "beable" to represent whatever exists in "the universe of discourse". Thus, for me: "superimposed quantum states exist in quantum theory" -- being epistemic and not ontological. All my beables are therefore existents (ontological) in spacetime; spacetime being my universe of discourse.
Alas, going beyond some shared beliefs, I suspect we share this defect: "Now after reading also some other essays I find that I expect the reader (that does not know me) to trust me too much and to follow me in my thoughts. That is too much to expect." In my case, I expected my readers to follow some elementary math and draw some interesting conclusions without prompting. [nb: to partially remedy my defect, and to help you, I will add a brief BACKGROUND note to my thread. I'll let you know when it's up.]
However, modifying one of your comments to fit my case: I tried hard to find the underlying reality, that explains these quantum phenomena WITHOUT introducing any ad hoc mechanism that does the job.
Also, you say: "I always liked Bohr." I say: I always liked Einstein.
However, as you say: "Bell and Einstein are the ones that are nearer to our thinking on what is real [imho, because Bohr is often hard to fathom]. So when I try to defend Bohr, I always have in mind Bell and Einstein, to explain how Bohr could have been right."
But note here (re the disposition of the whole apparatus; and without any nonlocality), I think that Bohr was right. Since interactions perturb sensitive objects, what we learn will be contextual because the context (eg, the paired-test-settings in EPRB = the disposition of the apparatus) will determine what we learn: HENCE (and critically) what we can reliably infer. BUT, relatedly, in my essay I show that Bohr was also right with his all-too-often-neglected "disturbance dictum".
Such a small comment by Bohr: BUT, as I show, THUS does Bohr eliminate many naive interpretations that talk of nonlocality or instantaneous collapse of the wavefunction!
And I agree with this: "As a realist I imagine the world consisting of fundamental things with properties, that are independent of whether they are observed or not." But I amend this next: "Of course some properties need to be inferable [not necessarily observable] in order to build the basis of a scientific theory."
Also: It looks to me that some of the math that you brought to your sheep would not be out of place with my essay.
With my thanks again, and best regards: Gordon
PS: Luca, if/when you reply to my post, please copy it to my essay-thread so that I'm alerted to it. I will do likewise.
Many thanks; Gordon Watson More realistic fundamentals: quantum theory from one premiss.
Dear Luca
If you are looking for another essay to read and rate in the final days of the contest, will you consider mine please? I read all essays from those who comment on my page, and if I cant rate an essay highly, then I don't rate them at all. Infact I haven't issued a rating lower that ten. So you have nothing to lose by having me read your essay, and everything to gain.
Beyond my essay's introduction, I place a microscope on the subjects of universal complexity and natural forces. I do so within context that clock operation is driven by Quantum Mechanical forces (atomic and photonic), while clocks also serve measure of General Relativity's effects (spacetime, time dilation). In this respect clocks can be said to possess a split personality, giving them the distinction that they are simultaneously a study in QM, while GR is a study of clocks. The situation stands whereby we have two fundamental theories of the world, but just one world. And we have a singular device which serves study of both those fundamental theories. Two fundamental theories, but one device? Please join me and my essay in questioning this circumstance?
My essay goes on to identify natural forces in their universal roles, how they motivate the building of and maintaining complex universal structures and processes. When we look at how star fusion processes sit within a "narrow range of sensitivity" that stars are neither led to explode nor collapse under gravity. We think how lucky we are that the universe is just so. We can also count our lucky stars that the fusion process that marks the birth of a star, also leads to an eruption of photons from its surface. And again, how lucky we are! for if they didn't then gas accumulation wouldn't be halted and the star would again be led to collapse.
Could a natural organisation principle have been responsible for fine tuning universal systems? Faced with how lucky we appear to have been, shouldn't we consider this possibility?
For our luck surely didnt run out there, for these photons stream down on earth, liquifying oceans which drive geochemical processes that we "life" are reliant upon. The Earth is made up of elements that possess the chemical potentials that life is entirely dependent upon. Those chemical potentials are not expressed in the absence of water solvency. So again, how amazingly fortunate we are that these chemical potentials exist in the first instance, and additionally within an environment of abundant water solvency such as Earth, able to express these potentials.
My essay is attempt of something audacious. It questions the fundamental nature of the interaction between space and matter Guv = Tuv, and hypothesizes the equality between space curvature and atomic forces is due to common process. Space gives up a potential in exchange for atomic forces in a conversion process, which drives atomic activity. And furthermore, that Baryons only exist because this energy potential of space exists and is available for exploitation. Baryon characteristics and behaviours, complexity of structure and process might then be explained in terms of being evolved and optimised for this purpose and existence. Removing need for so many layers of extraordinary luck to eventuate our own existence. It attempts an interpretation of the above mentioned stellar processes within these terms, but also extends much further. It shines a light on molecular structure that binds matter together, as potentially being an evolved agency that enhances rigidity and therefor persistence of universal system. We then turn a questioning mind towards Earths unlikely geochemical processes, (for which we living things owe so much) and look at its central theme and propensity for molecular rock forming processes. The existence of chemical potentials and their diverse range of molecular bond formation activities? The abundance of water solvent on Earth, for which many geochemical rock forming processes could not be expressed without? The question of a watery Earth? is then implicated as being part of an evolved system that arose for purpose and reason, alongside the same reason and purpose that molecular bonds and chemistry processes arose.
By identifying atomic forces as having their origin in space, we have identified how they perpetually act, and deliver work products. Forces drive clocks and clock activity is shown by GR to dilate. My essay details the principle of force dilation and applies it to a universal mystery. My essay raises the possibility, that nature in possession of a natural energy potential, will spontaneously generate a circumstance of Darwinian emergence. It did so on Earth, and perhaps it did so within a wider scope. We learnt how biology generates intricate structure and complexity, and now we learn how it might explain for intricate structure and complexity within universal physical systems.
To steal a phrase from my essay "A world product of evolved optimization".
Best of luck for the conclusion of the contest
Kind regards
Steven Andresen
Darwinian Universal Fundamental Origin
Dear Luca Valeri Zimmermann.
I have read your Essay wherein you briefly mention EPR. Einstein was right when he did not agree with the EPR experiment conclusions and had said, "spooky action at a distance" cannot occur and that, "God does not play dice". Please read Linear Polarization http://vixra.org/pdf/1303.0174v5.pdf
QM claims that an electron can be both spin-up and spin-down at the same time. In my conceptual physics Essay on Electron Spin, I have proved that this is not true. Please read: https://fqxi.org/community/forum/topic/3145
Kamal Rajpal
Hi Kamal
Thanks for reading my essay.
Just to clarify: The EPR reality criteria does not hold in the interpretation of quantum mechanics I gave in my essay.
And I really don't know, what it means, when someone claims, that the spin of an electron is up and down at the same time. In my essay I give the following interpretation for a spin in x-direction, which can be written as superposition of up and down in z-direction.
If one measures the z-direction of the spin, it can be found with 50% chance as up and 50% as down. If is found as up for instance I claim it really was up. We just did not know before. That is the meaning of the superposition.
If one measures the x direction of the spin he gets with certainty the spin in x direction. And the spin really was in the x direction, when measured! When not measured it was not. The spin property is only defined (and real) relative to the measurement settings.
The problem with this interpretation is, that different observers could claim to have different realities. This results in a loss of the objectivity and lead to many worlds, QBis or Rovellis relaional QM.
I claim in my essay to have solved this objectivity problem, while I still hold that the reality of the spin property is only given relative to the measuring setting.
Luca
Luca, from my essay-thread, in reply to your helpful comments: Gordon. ....
Hi Luca, and many thanks! [nb: below, the superscript-function does not work with ±. I use "bold" to identify the start of my comments; not for emphasis.]
I agree: "The disturbance interpretation is very appealing, since it maintains our realistic view of beables."
I acknowledge that many agree with you: "The formalism [I] use is not so transparent."
But this next from you gives me hope for the formalism: "However I think I got the idea." nb: the formalism is meant to be physically significant in that a beable is represented by the same physically significant symbol: objectively/ontologically in spacetime and abstractly/epistemically in the mathematics.
I thank you for this: "Where I see a problem is the link between formula (8) and (9). This needs more clarification. The source information (beta) disappeared. I can imagine, that this is because of the perfect correlation of the angular momentum (ref. 15.12). However from the observed polarization vector (ref. 15.10) the total information of the angular momentum (ref. 15.11) cannot be inferred completely. Hence the source (beta) should not disappear in the derivation of the conditional probability." Please note: I do NOT infer to the total information of the angular momentum; for (as you rightly say) such cannot be inferred completely under β. However, I can carefully infer to the equivalence relations: and here I use a weaker, more general equivalence relation than that used by EPR and many others (about which we seem to agree; which is good).
In addition, note that β in (8) specifies the conditions under which the related (immediately-preceding) argument must be interpreted. So β drops out when we interpret (8) correctly and arrive at (9). This is explained in ¶6.2-6.3; but let me add for greater clarity:
The physical significance of the argument in (8) is this. Under condition β (and thus using the equivalence-relations established under β, etc) we are asked to evaluate the (possibly-disturbing) interaction between a polarizer δb± and a polarized particle q(a-). And we need the probability that q(b+) is the outcome. But, via our equivalence relations, this interaction/probability is just that covered (already classically) by Malus' Law.
So we use Malus' Law, to write (9) immediately. And we write QED because our result is that confirmed by QT under β. HTH?
In reply to this: "I will come back to the disturbance interpretation - how I see it - another time. Only so much: causes and effects are not as unambiguous as they seem and the condition for the possibility to make inferences from a measurement might depend on conditions not included in the description of the experiment (for instance the environment, which must be separable from the system)."
Agreeing with EPR, every relevant beable must be included in our analysis. So if you follow the suggestion in ¶4.1 to Watson (2017d:§2) you will see that my (1)-(2) includes the beable of spacetime, here reduced to 3-space since time and gravity are not essential beables under β.
With my thanks again, I look forward to your further comments on my disturbance interpretation: and any other concerns, critiques, suggestions, etc. I cannot be offended and learn much from such.
Gordon Watson More realistic fundamentals: quantum theory from one premiss.
Luca,
Thanks for your note on mine. Just to confirm I returned with your score as promised. Hope you and the sheep get in.
Peter
Luca, as mentioned above: here's some background on my theory; Gordon.
Background to Wholistic Mechanics (WM)
Whereas QM emerged from the UV-catastrophe ca1905, WM emerges from the locality-catastrophe typified by John Bell's dilemma ca1965: ie, seriously ambivalent about AAD, Bell adamantly rejected locality. He later surmised that maybe he and his followers were being rather silly -- correctly; as we show -- for WM is the local theory that resolves Bell's dilemma [there is no AAD] and proves the Bellian silliness.
So WM begins by bringing just one change to modern physics: rejecting naive-realism, true realism insists that some beables change interactively, after Bohr's disturbance-dictum. Thus recognising the minimum-action associated with Planck's constant, WM then recognises the maximum speed associated with light: for true locality insists that no influence propagates superluminally, after Einstein.
The union of these two classical principles -- the foundation of WM -- is true local realism (TLR). Under TLR, EPR's naive criterion for "an element of physical reality" is corrected, then the Laws of Malus and Bayes are validated in the quantum world. Then, via the R-F theorem ca1915, Born's Law is seen to derive from elementary Fourier theory. This in turn allows us to understand the physical significance of Dirac's notation; etc. Thus, beginning with these elementary natural principles, WM's universe-of-discourse focuses on beables in spacetime: with mathematics taken to be our best logic.
NB: Formulated in 1989 in response to a challenging article by David Mermin (1988), many leading Bellian physicists and philosophers have committed to review the foundations of WM and its early results. Since no such review has ever been delivered, I am not yet aware of any defect in the theory. Further, WM provides many ways to refute Bell's theorem (BT): one such is provided on p.8 of my essay.
PS: To those who dismiss my essay due to an alleged typo in the heading, I follow C. S. Peirce (absent his severity): "It is entirely contrary to good English usage to spell premiss, 'premise,' and this spelling ... simply betrays ignorance of the history of logic."
Assuring you that critical comments are most welcome,
Gordon Watson More realistic fundamentals: quantum theory from one premiss.
Here is a reply of mine on a comment William C. McHarris made in his blog and I would like to share in my blog.
Dear Bill,
Thanks for your comment on my essay. So far you are the only one commenting on my paragraph on free will. I really like that part of my essay, although it is very speculative. What I tried to do is to find a conceptual framework that makes it possible to think about free will. I don't think this is possible within a reductionistic realistic framework. No wonder that in that framework free will is not even definable and hence might appear as emergent or an illusion.
Yes, I take a orthodox view on quantum mechanics. But contrary to the orthodox view, I tread the measurement apparatus as quantum object. However by asking the object - measurement system to be separable from its environment (contrary to decoherence), the evolution on this system can be described as unitary and on the reduced states even as deterministic. Also conservation laws hold on the subsystem. Many words is not necessary, because the information transfer is objective. I think these are nice features of the presented model.
Of course, that the reality of the properties depend on the measurement system is the pill that one has to swallow. But I think this might be true in some extend for classical physics. Newtonian physics is only valid within an inertial reference frame. The reference frame itself remains undefined. Except one takes Poincare's view, where Newtons first law serves to define the linear momentum (and what a reference frame is). The second law then becomes an empirical law.
In my model (a bit different than the usual treatment of quantum reference frames) the measurement system is a field and has a double role. It serves as reference frame for the properties of the measured object and as a measurement systems, that gets information of the properties of the system.
Last but not least: I am really serious with my statement "whether a system is a classical system or a quantum system depends only on the symmetries of the system." The statement is true in a very trivial sense: If the evolution is invariant under phase changing (local gauche) transformations on the object subsystem (hence this transformation is a symmetry), then the phases are not observable and the properties are classical.
I belief that the statement is true also in more ambitious sense, that I cannot prove at the moment and might simply be wrong: every observable/measurable property is defined by a physical symmetry - where I call symmetry physical if there exists an evolution (depending only on the state of the environment), such that the changing of the properties of the object correspond to that symmetry. To show something like this would be nice. It could follow, that classical physics is not observationally complete. But there is much work to do here.
Thanks again for your comments. If you want to reply on the above please let me know on my blog.
Luca