Relative information at the foundation of physics by Carlo Rovelli

The above post was from me. I was logged out in no time at all!!!

Lorraine

Professor Rovelli,

As the eminence grise of these conversations, may I ask why physics favors the concept of information, over that of energy?

As living organisms, we are the result of billions of years of evolution. The

consequence of this process is two fairly distinct systems. One is the central nervous

system, to absorb, organize and act on information. The other, the respiratory, digestive

and circulatory systems, serve to consume and process energy. So we exist as

manifestations of this dichotomy of energy and information, as medium and message.

Since energy is conserved, old information is erased in the creation of new information. This gives rise to the "arrow of time."

We think of time as sequential events and the basis of cause and effect. Otherwise known as narrative and logic. The assumption these are effectively one and the same is flawed though. Does yesterday cause today, anymore than one rung on a ladder causes the next?

Cause and effect is due to the exchange of energy, usually significantly altering any information it may have conveyed. In the instance of days, the sun shining on a rotating planet creates the sequence called days, where it is not some point of the present proceeding through the sequence, but the changing configuration of the energy causing the sequence to form and dissolve, thus future becoming past. Tomorrow becomes yesterday, rather than anything other than a personal or subjective vector from yesterday to tomorrow.

While physical laws determine the outcome of any particular situation, the physical input into any event is only completed by the occurrence of the event, therefore precluding full knowledge of any event to a particular frame. Not only that, but as the past is no longer physically real, any events were often a matter of subjective perspective and any such perspective changes with time, the past can only be said to have occurred, without a truly definitive, objective knowledge of what did occur. So the notion of determinism is epistemic at best.

And the sanctity of information does seem based on this assumption of some form of "blocktime" determinism.

One would think that if time were a vector from past to future, the faster clock would move into the future more rapidly, but the opposite is true. Since it ages/burns quicker, it recedes into the past more rapidly.

Time and temperature are like frequency and amplitude; Descriptions of the energy.

I think we need to get back to basics.

Regards,

John Merryman

That second paragraph broke into line breaks because I cut and pasted it from my own essay.

Carlo,

thanks very much for your reply, but I must disagree with your reasoning.

I would contend that there is no dividing line between "the underlying physical" reality and the "high level" reality. There is a difference in complexity, but there is no difference in the essential nature of reality between the high level and the underlying level. No new properties can miraculously appear ex nihilo at the "high level" that do not have foundations in "the underlying physical" level.

So if the underlying reality is completely deterministic, then the "high level" is exactly the same. Determinism means that (due to laws of nature) only one physical outcome is possible for each next moment in time. That is, at the high level, no "choice and responsibility" is possible for human beings in a deterministic universe. Surely, in a deterministic universe, to believe that "choice and responsibility" is possible is to deceive oneself.

Cheers,

Lorraine

Dear Professor Rovelli,

While you tell an enjoyable tale and make a good point; I found your essay a bit disappointing, playing as it does upon the common misconceptions about entropy, and the confusion that exists about the extent to which the different types of entropy are interchangeable. Of course; the Scientific American editors did it too, when they ran an article about non-linear entropy in the mesoscale regime by J. Miguel Rubi, by proclaiming on their cover that his studies show how nature breaks the 2nd law of thermodynamics. However; if you read Rubi's version, he carefully explains that thermodynamic entropy steadily increases while the system displays alternating regimes of chaotic and orderly forms - in apparent defiance of the 2nd law. Or at least that defiance is what appears true for those who equate entropy with disorder.

Personally; I prefer the spreading metaphor championed by Leff, for thermodynamic and mixing entropy. It seems that due to efforts by Lambert and others, the 'entropy is disorder' description is almost completely absent from Chemistry textbooks, as it brought confusion and was distracting from the thermodynamic aspects of Chemistry, but in Physics this idea of energy dispersal being associated with thermodynamic entropy was kind of skipped over as statistical models based on information were broadly adopted or already in use. Still; it is arguable that the specific meaning defined by Clausius was already changed somewhat by Boltzmann, when he suggested that disorder's increase was associated with growing entropy, but that not all entropy is the same.

Also; I think it is often glossed over that there is a specific n involved, the number of molecules in molar volumes of gases, which has the effect to make the system under study quantum mechanical. When there is a discussion of microstates, it is in terms of equivalent microscopic state changes which are all equally possible because they yield the same macroscopic condition. It is as though nature is performing one mother of a path integral, while we are just reading the temperature and pressure on a gauge. I think nature's way of defining things is indeed through relative information, and you have done a wonderful job of conveying this. The constrained system could consist of cranks and pistons, or it could be a pair of entangled particles where one has been partially measured.

So your essay was enjoyed, but confusion about entropy is a bugbear for me, and I think your conclusion stands just as well without need for confusing the issues.

All the Best,

Jonathan

Dear Professor Rovelli - I am always inspired by your papers (and books); this essay is no different. Your review of entropy is very enlightening. It was perhaps an accident that I read your paper back to back with the essay by Christian Corda, in which he says something very similar:

[from Corda] "In principle, a process in which pure states evolve in completely mixed states does not contradict the laws of quantum mechanics because the apparent information loss is instead hidden by quantum entanglement. The term entanglement means that the quantum state of a quantum system composed by two (or more) subsystems depends on the quantum state of each subsystem even if they are spatially separated. When one sums up the information in the two subsystems the result will be less than the information in the original system. The apparent information loss results hidden inside correlations between the subsystems."

My favorite paragraph form your paper was: "Thus, the systems formed by atoms have necessarily information about one another in the sense of Shannon. The negative information (in this sense) that a system have about another is precisely the relative entropy of the second, which is relevant for the interactions with the first, and is the conventional thermodynamical entropy."

In my essay I introduced an idea that might first seem absurd. A trapped photon bouncing back and forth between two atoms will trap energy/information, and for all intents and purposes will be "dark", i.e. outside of (classical) time. I introduce the concept of subtime to describe relative reversible evolution between measurements; much of this was inspired by your earlier writings.

I think you will find this idea to be quite different to thermal time and Tomita flow. I would be honored to receive your thoughts after reviewing it.

Kind regards, Paul

Hi Carlo,

Thank you for such a clearly described investigation into the fundamentals. I especially like these:

> If they are like letters of an alphabet, to whom do they tell stories?

> The world is not just a blind wind of atoms, or generally covariant quantum fields. It is also the infinite game of mirrors reflecting one another formed by the correlations among the structures formed by the elementary objects.

In my essay Software Cosmos I show how we might work within the simulation paradigm to model a world of information. This discrete computational cosmos has properties that we observe of our own, and in fact, I have carried out a test to see whether we now inhabit such a world.

Interestingly enough, a world constructed of information has room for more than the "blind wind of atoms". Different architectural layers of the software cosmos can have quite different properties. The layers of Life and Mind can lie below the physical layer of Matter, and not be (as conventionally assumed) emergent from it. Life and Mind, then, can animate Matter, and so produce the phenomenology of consciousness.

I hope you get a chance to read my essay, as I would love to know what you think of my model.

Hugh

Dear Carlo:

What a well written essay. I enjoyed reading it a lot. I usually hate it when people use these comments to immediately point to their own essays but here it seems appropriate and here is why: You point out that thermodynamic quantities depend on a coarse graining and that the proper coarse graining is determined by how the two systems interact with each other. In the example of the box of differently colored and charged balls you then discuss the possibility that there could in fact be different coarse grainings. Maybe there is a way to interact with the broken cup on the floor that makes it look like it has less entropy than the whole cup. My point now is this:

There is a special interaction between the two systems. Not all conceivable interactions are relevant. One of them is singled out.

The interaction that is relevant is the one that is mediated by the generalized rigidity of the systems (I point this out in my essay). For the cup this generalized rigidity is the rigidity of the lattice of molecules that makes up the cup (this is original example of rigidity). If you kick it, it kicks back. There is just one of these and it chosen by the dynamics of the molecules not by the observer.

If you think about the classical examples that one finds in thermodynamics you can see the same thing. The volume of a system is relevant because of the rigidity of the box that encloses the volume. We interact with the piston in a certain way again because of its rigidity etc.

So I think that you are pointing to an important fact but you are missing one half of the story: there is a special interaction.

Cheers

Olaf

Dear Carlo,

We are at the end of this essay contest.

In conclusion, at the question to know if Information is more fundamental than Matter, there is a good reason to answer that Matter is made of an amazing mixture of eInfo and eEnergy, at the same time.

Matter is thus eInfo made with eEnergy rather than answer it is made with eEnergy and eInfo ; because eInfo is eEnergy, and the one does not go without the other one.

eEnergy and eInfo are the two basic Principles of the eUniverse. Nothing can exist if it is not eEnergy, and any object is eInfo, and therefore eEnergy.

And consequently our eReality is eInfo made with eEnergy. And the final verdict is : eReality is virtual, and virtuality is our fundamental eReality.

Good luck to the winners,

And see you soon, with good news on this topic, and the Theory of Everything.

Amazigh H.

I rated your essay.

Please visit My essay.

Your essay was nice and short. It provided an eloquent, overarching argument for why information is very important in physics. And how, exactly, it is built into the foundations of the physical world. However, I think you sort of neglected the question posed in the essay prompt. It is clear, in my opinion, that "bits" and "its" are both in the foundation. They are are both very fundamental concepts. The question was/is what is more fundamental. I suggested in my essay that force(s) are even more fundamental than both, i.e., its and bits from forces.

Please check out my essay: All Your Base Are Belong To Math.

- Kyle Miller

Dear Carlo,

Thank you so much for your interesting essay. I doubt your last section on relativity based on the Shannon-sense information. As also mentioned in my essay, http://fqxi.org/community/forum/topic/1836 , Shannon originally consider the amount of information can be taken as the optimal compression rate of bit sequences. In relativity sense, this connection is not trivial. From this viewpoint, it seems to be conceptually mismatched. What do you think?

Best wishes,

Yutaka

Dear Professor Rovelli,

I agree with you, "The universe is not just simply the position of all its Democritean atoms." I agree further that, if this be true, then the

additional facts (i.e., the facts which go beyond the simple Democritean-atomic facts) have to be objectively "out there." The additional facts

should not be just subjectively projected onto the cosmos. Finally, I agree that the crucial issue then becomes how to identify the appropriate

macrostates. What coarse-graining does nature use? What is the "real" way to group microstates into macrostates? Your illustration about color

and electric charge clarifies the problem.

However, your proposed solution seems incorrect. You argue that interaction with an external physical system brings about the requisite

organization. But surely, the correct answer is that "physical constraints" provide the order. These I take to be laws and categories of

nature. The laws of nature hold true, prior to any interaction between two systems and even in the absence of all interactions.

One way to see what I am saying is to think about the metaphor of messages formed from letters of the alphabet. You ask, "If they [Democritean

atoms] are like letters of an alphabet, to whom do they tell stories?" This is an important question, but the relevant question is a different

one. We should ask instead, Why are some combinations of letters stories, while other combinations are gibberish? In stories, there are at

least three levels of structure. These are the constraints of vocabulary, the constraints of grammatical rules, and then the need to tell a coherent story and make sense. In the world, nature furnishes analogues of at least the first two of these. Perhaps the operations of nature

are so restricted that the world also objectively contains at least part of the analogue of the third.

If we locate the principles for coarse-graining in objectively-given laws rather than in interaction with something external, then we can think

that it makes sense to speak of the information content of the entire universe. One reason to believe that this does make sense is that we

should then be able to compare the actual universe to merely possible universes.

So then, are the Democritean atoms like "an immense alphabet so rich to be capable of reading itself and thinking itself"? The answer depends on

where we think the richness is located. If we think the richness is in the atoms, the answer is "No". If we think the richness is in both the

atoms and the rules which constrain how the atoms behave and combine, then the answer appears to be "Yes". The complex structures of the world

are not merely concatenations of atoms, nor do these structures "emerge" from concatenations per se. Rather, the complex order of the world

results from very specific properties, relations, and rules which were in the world from the beginning.

Laurence Hitterdale

Carlo,

The only conclusion I can come to from what you are saying is that future physical outcomes are already fixed and set in stone. This is the picture of the nature of reality painted by determinism i.e. by the view that living things are, in essence, mechanisms like the automatic speed control in a car.

(Of course although we can estimate probable/possible future outcomes, we usually can't know what future physical outcomes are going to be because of complexity. But complexity is a separate issue)

I think we must agree to disagree about the nature of reality!

Cheers,

Lorraine

Professor Rovelli ,

I am sure You do not Know who I am, as many other

participant.

Let me say , to be in this contest is an historical goal.

Can I ask to read my essay for some opinion?

Into my best hope, the basic idea of the script is a "classic law"

for quantum physics. Well, I need suggestions about the idea.

http://fqxi.org/community/forum/topic/1903

My Best Regards. Giacomo Alessiani.

Late-in-the-Day Thoughts about the Essays I've Read

I am sending to you the following thoughts because I found your essay particularly well stated, insightful, and helpful, even though in certain respects we may significantly diverge in our viewpoints. Thank you! Lumping and sorting is a dangerous adventure; let me apologize in advance if I have significantly misread or misrepresented your essay in what follows.

Of the nearly two hundred essays submitted to the competition, there seems to be a preponderance of sentiment for the 'Bit-from-It" standpoint, though many excellent essays argue against this stance or advocate for a wider perspective on the whole issue. Joseph Brenner provided an excellent analysis of the various positions that might be taken with the topic, which he subsumes under the categories of 'It-from-Bit', 'Bit-from-It', and 'It-and-Bit'.

Brenner himself supports the 'Bit-from-It' position of Julian Barbour as stated in his 2011 essay that gave impetus to the present competition. Others such as James Beichler, Sundance Bilson-Thompson, Agung Budiyono, and Olaf Dreyer have presented well-stated arguments that generally align with a 'Bit-from-It' position.

Various renderings of the contrary position, 'It-from-Bit', have received well-reasoned support from Stephen Anastasi, Paul Borrill, Luigi Foschini, Akinbo Ojo, and Jochen Szangolies. An allied category that was not included in Brenner's analysis is 'It-from-Qubit', and valuable explorations of this general position were undertaken by Giacomo D'Ariano, Philip Gibbs, Michel Planat and Armin Shirazi.

The category of 'It-and-Bit' displays a great diversity of approaches which can be seen in the works of Mikalai Birukou, Kevin Knuth, Willard Mittelman, Georgina Parry, and Cristinel Stoica,.

It seems useful to discriminate among the various approaches to 'It-and-Bit' a subcategory that perhaps could be identified as 'meaning circuits', in a sense loosely associated with the phrase by J.A. Wheeler. Essays that reveal aspects of 'meaning circuits' are those of Howard Barnum, Hugh Matlock, Georgina Parry, Armin Shirazi, and in especially that of Alexei Grinbaum.

Proceeding from a phenomenological stance as developed by Husserl, Grinbaum asserts that the choice to be made of either 'It from Bit' or 'Bit from It' can be supplemented by considering 'It from Bit' and 'Bit from It'. To do this, he presents an 'epistemic loop' by which physics and information are cyclically connected, essentially the same 'loop' as that which Wheeler represented with his 'meaning circuit'. Depending on where one 'cuts' the loop, antecedent and precedent conditions are obtained which support an 'It from Bit' interpretation, or a 'Bit from It' interpretation, or, though not mentioned by Grinbaum, even an 'It from Qubit' interpretation. I'll also point out that depending on where the cut is made, it can be seen as a 'Cartesian cut' between res extensa and res cogitans or as a 'Heisenberg cut' between the quantum system and the observer. The implications of this perspective are enormous for the present It/Bit debate! To quote Grinbaum: "The key to understanding the opposition between IT and BIT is in choosing a vantage point from which OR looks as good as AND. Then this opposition becomes unnecessary: the loop view simply dissolves it." Grinbaum then goes on to point out that this epistemologically circular structure "...is not a logical disaster, rather it is a well-documented property of all foundational studies."

However, Grinbaum maintains that it is mandatory to cut the loop; he claims that it is "...a logical necessity: it is logically impossible to describe the loop as a whole within one theory." I will argue that in fact it is vital to preserve the loop as a whole and to revise our expectations of what we wish to accomplish by making the cut. In fact, the ongoing It/Bit debate has been sustained for decades by our inability to recognize the consequences that result from making such a cut. As a result, we have been unable to take up the task of studying the properties inherent in the circularity of the loop. Helpful in this regard would be an examination of the role of relations between various elements and aspects of the loop. To a certain extent the importance of the role of relations has already been well stated in the essays of Kevin Knuth, Carlo Rovelli, Cristinel Stoica, and Jochen Szangolies although without application to aspects that clearly arise from 'circularity'. Gary Miller's discussion of the role of patterns, drawn from various historical precedents in mathematics, philosophy, and psychology, provides the clearest hints of all competition submissions on how the holistic analysis of this essential circular structure might be able to proceed.

In my paper, I outlined Susan Carey's assertion that a 'conceptual leap' is often required in the construction of a new scientific theory. Perhaps moving from a 'linearized' perspective of the structure of a scientific theory to one that is 'circularized' is just one further example of this kind of conceptual change.

Carlo,

"The world is not just a blind wind of atoms, or generally covariant quantum fields. It is also the infinite game of mirrors reflecting one another

formed by the correlations among the structures formed by the elementary objects."

In "It's Great to be the King," I claim that this mirror is a telescope taking humankind back in time,access that enables us to visualize an anthropomorphic interpretation of reality.

I never thought of information being a unifying force and the assembling of atoms like an alphabet into a macro system. I like the idea of selected structures defining finality but not reality.

You have a more nuanced concept of It and Bit.

Jim

Your comment that the Universe is the net information that all systems have about one another seems to be the Machian Principle regarding the global affecting the local. A network of dynamic space-time would create this, everything would be connected to everything else (and the interactions create information). In my essay I have assumed such a model to create matter from dynamic space. However I was interested in your comment that a dynamical space-time is necessarily discrete. As a last minute questons can I ask why this is so?

I enjoyed your essay. Thank you

Carolyn Devereux