Dear Carlo,

A concept that information is a relative phenomena goes against classical and intuitive view of the world, to the point that even well-meaning grads still try to find a "universal underlying information", were none is present. Not further then one month ago we had such conversation, in two long batches of posts in this very competition at http://www.fqxi.org/community/forum/topic/1597 with Jochen. My use of magic words "Relational Quantum Mechanics" did not trigger at all that "all information is relative", or "there is no underlying universal information/reality", however obvious it may be in my own mind. Yet, in a longish back-and-forward, in a second batch, we came to a little formalism for highlighting the relative nature of information, and, therefore, descriptions. It seemed useful in driving information-relativity point. We even used Schmidt decomposition to provide a bridge between different informational perspectives.

Reading your paper from 1996, which is a 2nd reference in your essay, I like your "... keep in mind that the observer can be a table lamp". I am using in discussions a qubit as an observer, the "smallest" observer in informational sense.

In the 96's paper you had to tame notions of system and system's state, clarify and expose ambiguities. In the essay http://www.fqxi.org/community/forum/topic/1597 we make a guess of what is there in reality, taking cues from seemingly infallible QFTs of Standard Model. Then a notion of system becomes effective, and restricted by initial definitions, removing many common problems (e.g. cannot have priviledged systems, making all same). Then, we ask a question about information flow between interacting and non-interacting systems, which is settled by looking at exepriment, leading to "interaction confinement" concept. Interaction confinement automatically translates into unitary evolution of closed system, and implicitly shows that description and information are relative, using your more exact words. I wonder how we may combine these concepts better to further the common cause for having even smoother description of QM phenomena.

Cheers,

Mikalai.

    Carlo,

    I find that your statement, "Amon all systems, living systems are those that selection has lead to reproduce continuously their own structure by, in particular, making use of the information they have about the exterior world. This is why we can understand them in terms of finality and intentionality, because they are the ones that have permaned thanks precisely to the finality in their structure. Thus, it is not finality that drives structure, but the other way around, selected structures define finality." is indeed factual.

    I have obtained evidence of what you have summarized about selected structures to map gravity with the strong, weak, and electromagnetic forces as one super-deterministc force. I invite you to review my findings and rate my essay when you get the chance:

    http://fqxi.org/community/forum/topic/1809

    Good luck with your entry of which I have rated highly for its insight.

    Regards,

    Manuel

    Dear Carlo Rovelli,

    I was very pleased to read your essay. Indeed, the context of a system has tremendous impact to the system, if we are interested in information, entropy, quantum mechanics, etc. Local depends on global, everything is relative to the context. I like your bold view that the context impacts reversibility even more than the intrinsic properties of the system. I find this natural for small systems, but for large systems is not that obvious, although, as you said, nothing prevents it from being true. As a parenthesis, John Baez just started an interesting series on relative entropy. About the interpretation of quantum mechanics you propose, I like the principle "It is always possible to acquire new information about a system." Each measurement resets the observed system to an eigenstate of the new observable, apparently acquiring new information, and, as you said, part of the old information becomes irrelevant. The system is forever fresh. This reminds me what Moisil said when he asked for a second glass of wine: "every man is entitled to a glass of wine, but after a glass of wine, you are a new man". On the other hand, I would like to make a comment on this, which I consider to be in the spirit of the relativity on the environment you advocate in your essay. The freshness of the system can very well be fueled from the unknown initial conditions of the system combined (and entangled) with the devices with which it previously interacted. If this is the case, the apparent acquiring of new information about the system is in fact acquiring of information about the continuously increasing system obtained by accounting all previous interactions. This becomes somewhat analogous to a classical, mechanical random generator (e.g. a pair of dice), where the freshness of the new randomness occurs by dissipating the previous one in the environment. I am not advocating the view that quantum phenomena can be explained by a classical picture, at least not without allowing the initial conditions to depend on the measurement context.

    I think your following remark in the concluding section sheds new light on "it from bit": "The universe is not just simply the position of all its Democritean atoms. It is also the net of information that all systems have about one another."

    Best regards,

    Cristi Stoica

      Dr. Rovelli,

      Hi. Good essay! I do have one question, which may stem from my lack of knowledge, but if, as you say, "the information relevant in physics is always the relative information between two systems", how can there be information about the universe, or existence, as a whole because there shouldn't be another system outside the universe with which it can interact. Would the second system be an arbitrarily imposed size for the universe?

      Also, there are tons of essays, but any feedback you might have on mine would be most welcome. It's at

      http://fqxi.org/data/essay-contest-files/Granet_fqxiessay2013final.pdf

      and is basically about the idea that maybe we shouldn't argue so much about it or bit, analog or digital, etc., but should just accept that there is some generic existent state at the heart of existence and try to figure out how such an existent state can lead to the universe we see around us.

      Anyways, I enjoyed reading your well written essay! Thanks!

      Roger Granet

        Dear Carlo Rovelli,

        Thanks for your very interesting essay. You make the point that information is relative. Linguistics, applied to informatics, tells us something very similar: A bit, implemented in computer hardware, is at first merely an abstract symbol without any meaning. Only, when we assign a meaning (semantics) to the bit, by agreeing that, e.g., it shall refer to the nth digit within a binary number, we can say that the bit carries information. So, at least on the binary level, information is always relative to an "agreement" or, in physical terms, relative to a "frame of reference". I think, this is in line with your position, although in a more abstract sense.

        Now, being physicists, we are inclined to ask: What happens to the information contained in a bit, when we change the frame of reference? I have studied this question in my essay and encountered informational structures that qualitatively and quantitatively resemble the basic structures of elementary particle physics - similar to your findings.

        Any feedback you might have on my essay would be most welcome.

        Walter Smilga

          1) No, you cannot make the entropy go up much. If you control the temperature, then this means that the system remains in equilibrium with a heat bath. At fixed temperature, if you add new energy, this is just going to go out as heat, so, there is no way you can increase S after it got to the maximum.

          2) I do not think "space" is just a separator, if by "space" we mean what we mean in general relativity. It is more than that. In particular, it carries quantities that are expressed by the metric field. So for instance the space between two walls is not just the separation between the two walls: it also how many *meters* are there between the two walls. Now, in general relativity this is just the *amount of gravitational field* between the walls, because distance is a function of the gravitational field. Therefore what can be discrete is not the "separator" is is the gravitational field that determine this distance. The point is that there is no separation less than a minimal one.

          3) There is a difference between atoms and monads. Atoms (in ancient atomism) have only their shape and relative position and order. Monads are much more complicate things, that can reflect the external world and hold a vision of the rest of the universe. I am fascinated by Leibniz ideas, but I also think that one should move ideas around with care.

          Thanks for your comments!

          Thanks for everything. I did not know about Baez. I go look at that that. c

          In fact, I do think that it makes no sense to talk about the "relevant physical information" for the entire universe!

          Dear Walter, thanks for this comment. I think that it is better if physics does not mix the two levels. The reason I refer constantly to Shannon's definition of information is that his definition is independent from semantics, as Shannon himself emphasizes in his 1948 work. The point I am trying to make is precisely the fact that there is are meaningful notions of information and relative information in simple physics, without need to refer to semantic, meaning, or mental or idealistic perspectives.

          c

          Dear Carlo,

          thanks for your response. Certainly, Shannon gave a definition of information that is independent from semantics and this is a great intellectual achievement. However, physics generally deals not with abstract information, but with information about physical things, e.g., spin, position, mass. With my understanding of the word semantics, it therefore deals with information relative to a semantic frame of reference.

          Of course, I agree with you that physical laws shall be formulated independent from a specific frame of reference and this includes also semantic frames of reference. However, to ensure this independency we must formulate them in such a way that the laws can easily be adapted to any specific frame of reference, whenever for practical reasons this is required.

          Therefore, even though the laws do not refer to a specific frame of reference, we must implement the possibility to adapt the law to any specific frame of reference. This includes that we must be able to tell how this adaptation changes with a change of the frame of reference.

          This consideration has motivated me to study the structure of binary information relative to a "semantic frame of reference", which I regard as a straight-forward generalization of the notion of a coordinate system.

          Regards,

          Walter

          Dear Dr. Carlo Rovelli,

          I have down loaded your essay and soon post my comments on it. Mean while, please, go through my essay and post your comments.

          Regards and good luck in the contest.

          Sreenath BN.

          http://fqxi.org/community/forum/topic/1827

          Dear Carlo Rovelli,

          Your suggestion to use Shannon's relative information at the foundation of physics may be very courageous after the use of relative information seems to be inappropriate for most ecological applications. Cf. R. K. Peet (1975) Relative Diversity Indices, Ecology 56, 496-498.

          Good luck,

          Eckard

            Dear Cario,

            Thank you for presenting your nice essay. I saw the abstract and will post my comments soon.

            So you can produce material from your thinking. . . .

            I am requesting you to go through my essay also. And I take this opportunity to say, to come to reality and base your arguments on experimental results.

            I failed mainly because I worked against the main stream. The main stream community people want magic from science instead of realty especially in the subject of cosmology. We all know well that cosmology is a subject where speculations rule.

            Hope to get your comments even directly to my mail ID also. . . .

            Best

            =snp

            snp.gupta@gmail.com

            http://vaksdynamicuniversemodel.blogspot.com/

            Pdf download:

            http://fqxi.org/community/forum/topic/essay-download/1607/__details/Gupta_Vak_FQXi_TABLE_REF_Fi.pdf

            Part of abstract:

            - -Material objects are more fundamental- - is being proposed in this paper; It is well known that there is no mental experiment, which produced material. . . Similarly creation of matter from empty space as required in Steady State theory or in Bigbang is another such problem in the Cosmological counterpart. . . . In this paper we will see about CMB, how it is generated from stars and Galaxies around us. And here we show that NO Microwave background radiation was detected till now after excluding radiation from Stars and Galaxies. . . .

            Some complements from FQXi community. . . . .

            A

            Anton Lorenz Vrba wrote on May. 4, 2013 @ 13:43 GMT

            ....... I do love your last two sentences - that is why I am coming back.

            Author Satyavarapu Naga Parameswara Gupta replied on May. 6, 2013 @ 09:24 GMT

            . . . . We should use our minds to down to earth realistic thinking. There is no point in wasting our brains in total imagination which are never realities. It is something like showing, mixing of cartoon characters with normal people in movies or people entering into Game-space in virtual reality games or Firing antimatter into a black hole!!!. It is sheer a madness of such concepts going on in many fields like science, mathematics, computer IT etc. . . .

            B.

            Francis V wrote on May. 11, 2013 @ 02:05 GMT

            Well-presented argument about the absence of any explosion for a relic frequency to occur and the detail on collection of temperature data......

            C

            Robert Bennett wrote on May. 14, 2013 @ 18:26 GMT

            "Material objects are more fundamental"..... in other words "IT from Bit" is true.

            Author Satyavarapu Naga Parameswara Gupta replied on May. 14, 2013 @ 22:53 GMT

            1. It is well known that there is no mental experiment, which produced material.

            2. John Wheeler did not produce material from information.

            3. Information describes material properties. But a mere description of material properties does not produce material.

            4. There are Gods, Wizards, and Magicians, allegedly produced material from nowhere. But will that be a scientific experiment?

            D

            Hoang cao Hai wrote on Jun. 16, 2013 @ 16:22 GMT

            It from bit - where are bit come from?

            Author Satyavarapu Naga Parameswara Gupta replied on Jun. 17, 2013 @ 06:10 GMT

            ....And your question is like asking, -- which is first? Egg or Hen?-- in other words Matter is first or Information is first? Is that so? In reality there is no way that Matter comes from information.

            Matter is another form of Energy. Matter cannot be created from nothing. Any type of vacuum cannot produce matter. Matter is another form of energy. Energy is having many forms: Mechanical, Electrical, Heat, Magnetic and so on..

            E

            Antony Ryan wrote on Jun. 23, 2013 @ 22:08 GMT

            .....Either way your abstract argument based empirical evidence is strong given that "a mere description of material properties does not produce material". While of course materials do give information.

            I think you deserve a place in the final based on this alone. Concise - simple - but undeniable.

            Hi Carlo, Dear Prof Rovelli

            On june 22, I sent you a post on this thread, perhaps you did not remark it because it was in the beginning, I am sill awaiting your very valued remarks.

            best regards

            Wilhelmus

              Dear Carlo,

              Want to point a recent article http://arxiv.org/abs/1306.5471 with a very meticulous treatment of quantum theory and phenomenology. These guys actually come to realisation that at a fundamental, or postulate level "... All that we can assume is a fundamental quantum field ..."

              Taking in your view of information (its creation and destruction by qm systems), and mine http://www.fqxi.org/community/forum/topic/essay-download/1597/__details/Birukou_Birukou_essay_Bit_I.pdf, all of it combined may finally give a sweet thing :)

              Mikalai

                Eckard, is there an online version of the article you quote? We do not get that kind of journals in our physics lab. Or maybe could you explain the main point? Thanks, Carlo

                Thanks for point out this rather interesting book. Carlo

                Thank you, Wilhelmus. Well, I di not reply because it was more a question to Ashtekar than to myself... c

                Thanks Carlo for replying...

                On 1), I did not mean to regulate the temperature during the entropy increase, but the temperature AT the time of energy introduction. From that equation, which I presume correct since you dont question it, if T is made very, very, very low, will the resulting entropy change following a small energy introduction not be very, very, very large?

                On 2), I didnt want to mix up discreteness with gravitational theory. To avoid confusion, discreteness implies occurring in separate representations, so that we can count 1, 2, etc. What usually enables us to do this, e.g. for grains of sand is separation by space. Or if you like let us take the space far away from any walls or gravitational field, in order not to argue over the statement "...because distance is a function of the gravitational field", will that far away space have a discrete nature?

                On 3), Leibniz did not originate Monads, the Pythagoreans did. Also apart from the initial 8 paragraphs of his Monadology, the remaining were more concerned with spiritual not with physics. Interestingly, an essayist here pointed out a reference that Wheeler suggested that his "elementary quantum phenomenon" was like a monad (JA Wheeler, The computer and the universe, International Journal of Theoretical Physics, vol.21, nos. 6/7, 1982)here.

                I know you are a busy academic, but if you have the time you may reply on these points.

                Regards,

                Akinbo