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

        @Carlo Rovelli: "... for all quantum systems, the orthogonal states are in finite number per each finite region of phase space." If there is a multiverse finite automaton then all possible measurable states are a finite set. If the multiverse is infinite and really needs an infinite phase space, then what is the explanation for the space roar? The space roar is supported by: FIRAS and low frequency radio data, ARCADE2 and low frequency radio data, and combined data sets from ARACADE2 and FIRAS.

        http://asd.gsfc.nasa.gov/archive/arcade/pubs/arc2_apj_interp_2011.pdf INTERPRETATION OF THE ARCADE2 ABSOLUTE SKY BRIGHTNESS MEASUREMENT by M. Seiffert, D. J. Fixsen, A. Kogut, et al., The Astrophysical J., 734:6 (8pp.), 2011 June 10

        Is any quantum theory of gravity that contradicts the space roar guaranteed to be wrong?

        Dear Carlo -

        I'm very glad to see a new essay of yours revisiting some themes of Relational Quantum Mechanics. I've always considered that paper a milestone, or rather a signpost pointing a way that remains to be explored. Maybe the time is ripe... there are a few other essays in this contest - Knuth's, for example - working with the idea that all of physics concerns "the information systems have about other systems."

        I very much agree with your conclusion - "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. Objects are not just aggregates of atoms. They are particular configurations of atoms singled out because of the manner a given other system interacts with them."

        However, I agree with Walter Smilga's comment above - in order to grasp what it means for things to have information, even in physics, we need to deal with contexts of meaning. You want to stick with Shannon's definition, as you wrote, to show "that there are meaningful notions of information and relative information in simple physics, without need to refer to semantic meaning." As in the RQM paper, here also you define "having information about" a system just as "being correlated" with it. (Knuth's contest essay likewise uses an abstract notion of systems "influencing" each other. And even Smilga, who wants to bring semantics into the picture, uses a very generalized notion of "semantic frames of reference.")

        I don't doubt that your approach gets at something very important about the structure of physics. But the point of my essay is that something else that's important is missed when we abstract from the specific kinds of contexts in which information actually becomes measurable.

        These contexts are not mysterious - we know all about how to assemble them when we make measurements. There's nothing subjective or mental about them - the same physics we use in the lab describes how any system gets information about other systems. But there are major obstacles to formulating any realistic general definition of a "measurement-context". It's not just that such arrangements are never physically simple, but also that any way of measuring something depends on other ways of measuring other things. I argue that this complex interdependency of different ways of "observing" is really what's behind the measurement problem in QM.

        In physics we're always trying to show how the underlying structure is basically simple - so the many different ways in which things actually "have information about each other" give us a picture that hardly seems as though it could be relevant to the physical foundations. Yet if we only think about abstract and generalized information-processes, we lose touch with the way information is physically present in the world.

        My suggestion is that measurement can be conceived as fundamental, if we can see it as an evolving process. Though it takes a very complex interactive environment to communicate definite information about and between its subsystems, this kind of environment can exist and maintain itself for the same reason that life does, if it's the kind of system that can evolve through random selection.

        Thanks again for the new essay - Conrad

          Dear Conrad,

          you touch something basic here. I agree that what you talk about is a central issue, and I am uncertain myself.

          We certainly agree on the relevance of context, and I feel everybody would agree, at least after a good discussion clarifying what we mean. But I have tried to bring this down to good old physics. You are right that in quantum mechanics this affects the measurement issue and you are right that it affects the definition of what is a measurement context. But the central point of Relational Quantum Mechanics is to solve this issue by accepting the idea that *any* physical interaction is a measurement. When an atom in a SternGerlack apparatus is deviated by the magnetic field, the position of the atom is measuring the spin. This seems to me the only possible solution; I have never found a convincing alternative. The price to pay is of course the Relational Quantum Mechanics observation that events are indexed by the context. That is, in this case the spin is measured by the position, and does not take value with respect to a system not interacting with it. This allows interference to affect possible later interactions with position or spin. Thus, in this sense I agree with you that measurement is fundamental, but I prefer to view it as synonymous of interaction, rather than trying to view it, as you suggest to attribute it to "a very complex interactive environment".

          Dear Carlo

          I read your essay with pleasure. It is very well written, clear, and easy to understand. I share essentially all points, though just at the qualitative level, i.e. as a general philosophy. I have been always curious about your relational quantum theory, and I now understand that it is meant to be an axiomatization program. That's is even more interesting for me, since, pragmatically, I do not pay much attention at the purely opinionated interpretational issues. I will consider to which of our axioms your postulates may be connected (I'm referring to the Pavia axiomatization http://pra.aps.org/abstract/PRA/v84/i1/e012311). I just downloaded your IJTP paper of 1996, and I notice a third axiom, which looks quite quantum. You don't mention it in your essay. Do you have a more recent version of your derivation of QT without it?

          Second, about LQG, it seems to me that, in a sense, you are not so far from my cellular automaton approach, and I was wondering if e.g. your loops maybe related to my loops on the Cayley graph. I'm very curious.

          My best regards

          Mauro

            Dear Dr. Carlo,

            Your essay is short but contains enough information on 'Information', but you haven't touched up on 'reality' in the same way; so I couldn't see your valuable views on reality and disappointed. I hope you will make it up to it soon.

            You have identified entropy with information, but is this identification universal? For example, if two systems are in equilibrium with each other there will be no change in the entropy of the two systems but yet there can be exchange of information between them.

            You have reviewed the current trend prevailing in physics to unite such different fields as thermodynamics, gravitation and quantum physics on the basis of the concept of entropy as yourself being one of the champions of LQG. There are lots of expectations to see how far you succeed in your endeavor.

            I also expect you to go through my essay and post your comments. http://fqxi.org/community/forum/topic/1827.

            Best regards,

            Sreenath

            Carlo - thanks for your response, and I get your point. In fact, I pulled out my old marked-up copy of the RQM paper and was reminded again what a thorough piece of work it is, given its limited scope. It lays out - more carefully than any work of philosophy I know of - the basic philosophical issues involved in the meaning of objectivity.

            It is just the notion that events are indexed by the observer-relative context that's important to me. The world only exists from the standpoint of some observer. This isn't subjective (mental), in that anything counts as an observer. It's not solipsistic, in that communication between observers is as fundamental as observation itself - in fact, from the QM viewpoint there's no difference between these two. But as you say, it's an error to describe this world of multiple observers as if it could be envisioned "from outside", from no point of view - as if there could be well-defined information without a context to define it from a specific point of view.

            This is a very radical notion, and I think it will be some time before we have the conceptual tools we need to be clear about it.

            So I understand your "only possible solution" - treating any interaction as a measurement. But I would remind you of the point you make in RQM, that even the correlation between two systems is only definable from the standpoint of a third system. And the position of the atom "measures" the spin, insofar as something else observes the atom, in some context in which its position is definable over time.

            There's no specific level of complexity at which interactions become measurements, or systems become observers. To that extent I agree, it's better to treat all systems as observers and all interactions as measurements. But this does not really "solve" any problem. Many different kinds of interactions are still needed to define / measure any physical information, and though I well understand your preference for "the good old physics", ultimately I think we can't set this fact aside as insignificant.

            In my essay I acknowledge the difficulty of dealing with it, and try to show how they can be addressed. In the end this points to a way of answering the basic question that's left - in my mind, anyway - by RQM: how and why do things work out so that at the macroscopic level, the quantum world of communicating observers ends up looking so much like the objective, deterministic reality of classical physics?

            Ok, you definitely convinced me to read with care what you have written! I will now print it out and study it... thanks! carlo

            Carlo,

            Interesting essay. As I dwell on the same questions you are raising I focused on the following statement you make:

            "The information contained in any fi nite region of the phase space of any system is fi nite."

            I would agree this is true to the level of precision allowed to the level of error imposed upon us by the uncertainty principle. However, the error does represent information, a vast amount of it, and it is this information that ultimately forces us to only accept an approximate reality. In general, I have to agree with Democritus that life is change. In general I think these ideas seem to be manifest in several of the essay provided. I was wondering what your thoughts are on the apparent prevalence of the same ideas?

            My essay if you're interested.

            Carlo,

            If given the time and the wits to evaluate over 120 more entries, I have a month to try. My seemingly whimsical title, "It's good to be the king," is serious about our subject.

            Jim