Essay Abstract

Traditionally, scientific enquiry has presupposed a relatively simple relationship between our empirical evidence and the facts of reality. For example, we presume that our memories and records are approximately correct representations of the actual course of past history, and we presume that most of the events which actually occur are events made either certain or probable by underlying physical laws. Such assumptions seem to be necessary if ordinary scientific methods of formulating deterministic or probabilistic laws are ever to get off the ground. But developments in the fields of both statistical mechanics and quantum mechanics have begun to give us specific reasons to question these assumptions, since both theories explicitly undermine our beliefs about the causal links between records of the past and actual past events. In light of such considerations, questions about the reliability of memories and records cannot be relegated to philosophical scepticism, but must be taken seriously as part of contemporary science and as indicators of possible new directions for the development of science.

Author Bio

Emily Adlam is reading Physics and Philosophy at the University of Oxford.

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  • Post #2

Clausius' famous principle "ENTROPY ALWAYS INCREASES" (which, according to A. Eddington, holds "the supreme position among the laws of Nature") was deduced in 1865 in the way presented by Jos Uffink on p. 37 in his "Bluff your Way in the Second Law of Thermodynamics":

http://philsci-archive.pitt.edu/archive/00000313/

Jos Uffink, Bluff your Way in the Second Law of Thermodynamics, p. 37: "Hence we obtain: THE ENTROPY PRINCIPLE (Clausius' version) For every nicht umkehrbar [irreversible] process in an adiabatically isolated system which begins and ends in an equilibrium state, the entropy of the final state is greater than or equal to that of the initial state. For every umkehrbar [reversible] process in an adiabatical system, the entropy of the final state is equal to that of the initial state."

Clearly Clausius' deduction is based on three premises:

PREMISE 1: The entropy is a state function.

PREMISE 2: Clausius' inequality (formula 10 on p. 33) is correct.

PREMISE 3: Any irreversible process can be closed by a reversible process to become a cycle.

All the three premises are unproven; PREMISE 3 is almost obviously false:

http://philsci-archive.pitt.edu/archive/00000313/

Jos Uffink, p.39: "A more important objection, it seems to me, is that Clausius bases his conclusion that the entropy increases in a nicht umkehrbar [irreversible] process on the assumption that such a process can be closed by an umkehrbar [reversible] process to become a cycle. This is essential for the definition of the entropy difference between the initial and final states. But the assumption is far from obvious for a system more complex than an ideal gas, or for states far from equilibrium, or for processes other than the simple exchange of heat and work. Thus, the generalisation to all transformations occurring in Nature is somewhat rash."

Pentcho Valev pvalev@yahoo.com

    Entropy and quantum mechanics are purely mathematical. In my opinion, applying such mathematical concepts to explain any physical system is incorrect.This leads to such ideas that question our belief regarding 'relationship between our empirical evidence and the facts of reality'.A clear demarcation between physics and mathematics will remove all such non-classical concepts.

    We require a physical definition of entropy.When the universe expands, the stars contract. This can be regraded as the entropy of the stars decrease when the entropy of the universe increases. This may be a reversible process.As long as the expansion continues, past will be past and future, future. If it starts contracting, it will be only a cyclical change and not a going back into the past.

      50 years ago the following challenges to the second law of thermodynamics would have produced a frenzy atmosphere in the scientific community. Nowadays scientists couldn't care less:

      http://arxiv.org/abs/1203.0161

      Self-Charged Graphene Battery Harvests Electricity from Thermal Energy of the Environment, Zihan Xu et al: "Moreover, the thermal velocity of ions can be maintained by the external environment, which means it is unlimited. However, little study has been reported on converting the ionic thermal energy into electricity. Here we present a graphene device with asymmetric electrodes configuration to capture such ionic thermal energy and convert it into electricity. (...) To exclude the possibility of chemical reaction, we performed control experiments... (...) In conclusion, we could not find any evidences that support the opinion that the induced voltage came from chemical reaction. The mechanism for electricity generation by graphene in solution is a pure physical process..."

      http://arxiv.org/ftp/arxiv/papers/1207/1207.6599.pdf

      "We have studied the Si devices to generate electricity from thermal motion of ions in aqueous electrolyte solutions at room temperature. (...) However,, this finding does not agree with the second law of thermodynamics, which limits the utilization of the random thermal motion of ions to be spontaneously collected to produce 10 electricity. We cannot explain why either this experiment or the previous experiment of graphene did not agree with the traditional theory. More research will be required to fully understand this phenomenon."

      http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.108.097403

      "Physicists have known for decades that, in principle, a semiconductor device can emit more light power than it consumes electrically. Experiments published in Physical Review Letters finally demonstrate this in practice, though at a small scale. (...) Decreasing the input power to 30 picowatts, the team detected nearly 70 picowatts of emitted light. The extra energy comes from lattice vibrations, so the device should be cooled slightly, as occurs in thermoelectric coolers. These initial results provide too little light for most applications. However, heating the light emitters increases their output power and efficiency, meaning they are like thermodynamic heat engines..."

      http://www.dailytech.com/An+Incredible+Discovery+Graphene+Transistors+SelfCool/article21285.htm

      "Overcoming technical challenges, the University of Illinois team used an atomic force microscope tip as a temperature probe to make the first nanometer-scale temperature measurements of a working graphene transistor. What they found was that the resistive heating ("waste heat") effect in graphene was weaker than its thermo-electric cooling effect at times. (...) Further, as the heat is converted back into electricity by the device, graphene transistors may have a two-fold power efficiency gain, both in ditching energetically expensive fans and by recycling heat losses into usable electricity. Professor King describes, "In silicon and most materials, the electronic heating is much larger than the self-cooling. However, we found that in these graphene transistors, there are regions where the thermoelectric cooling can be larger than the resistive heating, which allows these devices to cool themselves."

      Pentcho Valev pvalev@yahoo.com

      Dear Emily Adnam

      I appreciate your skeptical view of the nature of evidence, and how we must be cautious in this regard. However I do believe you are giving much too much credence to the Boltzmann Brain argument.

      You talk about the histories stored in our memories, but there is much more to history than that: it is for example also stored in the geological record, as well as in the radiation reaching us from the end of the hot big bang era nearly 14 billion years ago. You state "it is vastly more likely that the essay you are currently reading was produced by a random convergence of molecules than that at some time in the past another conscious person existed and wrote the essay." Do you really believe that? This depends on a whole series of extremely unlikely assumptions: inter alia equilibrium that lasted for almost an eternity of time, when there is no evidence this ever happened; the assumption that complex structures such as the brain can emerge from random fluctuations, when we've never even seen an amoeba emerge in this way, let alone a fly or a frog. It's a fun speculation, but I can't see how one can take it as very likely. The most that we can realistically expect to emerge from fluctuations are particles, or conceivably atoms.

      I fully agree with your criticism of the Everett interpretation, but then you kind of recant from that criticism. Why not assume there is indeed a collapse mechanism, we just don't know how it works? You say "the Everett interpretation might still, after all, be true." Well yes, but it might be false; the collapse hypothesis might be true. I can't see why that statement carries the day.

      It is good to have the reminder "transcendental considerations are frequently

      an important part of our scientific practice, but also they have their limits: even when we choose to rule out certain possibilities for practical reasons, we should view our avoidance of them not as rigid prohibitions but as useful heuristic guides for the present." Wise advice. This kind of meta analysis is very welcome: it is so often missing in physics writing.

      George Ellis

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        • Post #6

        Dear Emily Adnam

        What do you think about victimization second law of termodinamics?

        see http://fqxi.org/community/forum/topic/1413

          Hi Emily and George,

          I seem to be in the strange position of having to disagree with both of you. On the one hand, I agree with George that it seems a bit absurd to assume that the appearance of your essay from random fluctuations must be much more probable than were it to have been written by a conscious person. On the other hand, I agree with Emily that random fluctuations can nevertheless give rise to complex phenomena. My reason for both stances is the same: "highly improbable" is not the same thing as "impossible."

          This seems to be a common trait among humans in regard to our interpretation of statistical phenomena: an event that occurs is a priori assumed to be highly likely by dint of the fact that it has occurred in the first place. In light of additional information, the event's relative likelihood may be revised downward, but the fact of the matter is that it is initially assumed to be high simply because it happened. But even highly unlikely events still happen. My neighbor has been struck by lightning. If he grew up ignorant and isolated, he might be led to conclude that *everyone* gets struck by lightning which is absurd.

          In short, an equally valid interpretation is that our memories are perfectly valid and correct but that the universe simply evolved in a highly unlikely (but not impossible) way. For example, suppose there is a spectrum of *possible* universes (these would be *actual* universes in an Everettian interpretation). Even if only a single universe occurs, nothing says it absolutely must be one of the more likely candidates. That's the point of a random process.

          Also, one other point I wanted to make: entropy depends on how you define it. It is entirely possible to define it in such a way that a low entropy in the early universe is not unexpected.

          Regardless of my aforementioned gripes, it was a nice essay. I found it to be well-written and carefully considered.

          Ian Durham

          Emily,

          In your abstract, you state that:

          "scientific enquiry has presupposed a relatively simple relationship between our empirical evidence and the facts of reality... Such assumptions seem to be necessary... But developments ... give us specific reasons to question these assumptions."

          The simple relationship between evidence and reality, need not be questioned. Physical theories merely produce numerical predictions, that either agree or disagree with observations. They do nothing else. In particular, they provide no evidence, either for or against, all the metaphysical "interpretations" that have the attached to the theories. The theories can do little more than "fit curves to data", and they can only even do that, in cases where the data has an extremely low information content - that is what makes the data "predictable", by the theory, in the first place.

          Since the "interpretations of the theory" invariably have a higher information content than the theories themselves, the "interpretations" cannot possibly be contained within the theories themselves; they have simply been made-up and slapped-on. Hence, while experiments may confirm that the theory "fits" the data, they cannot provide any evidence that the "interpretation" fits the theory.

          Rather than questioning the "reliability of memories", physicists need to question the "meaning" and "significance" that they have attached to them.

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            • Post #9

            Thank you for your comments! It's certainly true that both the concept of entropy and the second law of thermodynamics are plagued with difficulties both in derivation and interpretation, and this essay is not intended to be a defence of either. My discussion of 'the entropy of the universe' is mainly a way of pointing to the appearance of temporal asymmetry - according to our memories and records there seems to be a kind of directedness in the way that events come about, yet that direction doesn't seem to come from the underlying microdynamics and therefore needs to be accounted for in terms of a further assumption about the initial conditions. It's convenient to frame that assumption in terms of the initial low entropy of the universe, but the argument isn't dependent on specific assumptions about the nature of entropy and/or the status of the second law.

            Thank you for this comment! I agree that it's certainly important to make a distinction between actual physics and the mathematics we use to formalize that physics, and it's true that the physical definition of entropy is problematic. I also agree that we would not start 'going back into the past' if the universe were to start contracting - the difficulty about the past that I wished to point to was merely that, based on standard dynamical theories and without addditional assumptions like the past hypotheses, retrodiction would suggest that 'entropy' (whatever that means physically) was probably higher in the past than it is now, and moreoever that it's difficult to see how our memories/records can directly testify against this.

            Thank you both for your replies!

            First, I'm sorry if I gave the impression that the difficulty with evidence is primarily concerned with memory. The same arguments apply to any kind of record of the past which is accessible in the present, including geological records and so on - it's still more likely that such records were produced by spontaneous fluctuations than that the past they purport to record actually happened (at least on a certain view of 'likelihood').

            I don't actually believe that the present state is just a fluctuation (I'm not sure it would be psychologically possible to believe that) but the difficulty is that it's hard to give a good justification for my conviction that the past actually happened as I remember it, given that all my reasons for believing that are based on memories and their veridicality is precisely the point at issue.

            We certainly can assume that there's some unknown collapse mechanism in QM, but again, there's a difficulty with justifying the claim. If the Everett interpretation is the simplest way of accounting for our present evidence, why not believe it? The logical difficulties that I point to in accepting the Everett interpretation don't seem to be the right kind of considerations to justify substantive physical claims about a collapse mechanism - surely we need more direct empirical evidence for something like that.

            Finally, I'd reinforce that the argument concerning entropy is really just a way of flagging up facts about temporal asymmetry, and isn't dependent on any particular definition of entropy. The problem is simply that in order to get retrodiction which match our memories/records of the past we apparently need to make some substantive assumptions about the nature of the initial state of the universe, and we don't seem to have an adequate justification for those assumptions, given that the theory suggests it's more likely those memories/records were formed in some alternative way. Perhaps the conclusion to draw is that we need to reassess our understanding of probability and typicality in these sorts of theories.

            While I would certainly agree that we need to be careful about differentiating between the content of a theory and its interpretation, I'd argue that theories can't be divorced entirely from 'interpretation' without rendering them incapable of making any predictions that can be compared to observation - at the very least, we need some specification of which mathematical features of the theory are meant to correspond to particular features of our evidence.

            Saying that physicists need to question the 'significance' of memory is a nice way of putting the point I want to make - that memories are just a form of data, and perhaps we need to stop interpreting that data quite so literally.

            Your statement that "we need some specification of which mathematical features of the theory are meant to correspond to particular features of our evidence" is exactly on target. It is discussed extensively in my own essay. Unfortunately, as I indicated there, making such a correspondence provides no evidence that it is correct.

            The problem is that the "meaning" of a high information content signal cannot be deduced from any observation of the signal, for the simple reason that "high information content" is synonymous with the fact that the signal itself is devoid of meaning. In effect, the signal is nothing more than a "serial number", whose "meaning" can only be deduced by "looking it up" within the memory of an entity that knows, a priori, the correspondence between the serial number and its "meaning's" address in memory.

            Physicists do indeed need to "stop interpreting that data quite so literally." Complex entities respond to data observations "symbolically" as well as "physically." Physical responses behavior as though data measurements are "real numbers", but symbolic responses behave as though they are "serial numbers." The entire information content of Physical behaviors can easily be represented, by short sequences of symbols, known as "equations." The vastly larger information content of the initial conditions, in the memory of a complex observer, cannot. For such observers, it is the initial conditions, not the equations, that determine all "interesting" behaviors, because that is the only thing that gives any meaning to observed "serial numbers."

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            • Post #14

            Emily,

            You wrote: "It's convenient to frame that assumption in terms of the initial low entropy of the universe, but the argument isn't dependent on specific assumptions about the nature of entropy and/or the status of the second law."

            But "initial low entropy" already presupposes some "specific assumptions about the nature of entropy and/or the status of the second law". By the way, at the end of his paper, Uffink in fact rejects the law of entropy increase:

            http://philsci-archive.pitt.edu/archive/00000313/

            Jos Uffink, Bluff your Way in the Second Law of Thermodynamics, p. 94: "This summary leads to the question whether it is fruitful to see irreversibility or time-asymmetry as the essence of the second law. Is it not more straightforward, in view of the unargued statements of Kelvin, the bold claims of Clausius and the strained attempts of Planck, to give up this idea? I believe that Ehrenfest-Afanassjewa was right in her verdict that the discussion about the arrow of time as expressed in the second law of the thermodynamics is actually a RED HERRING."

            Pentcho Valev pvalev@yahoo.com

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            • Post #15

            I believe that the act of contemplating the possibility of past intervention in human affairs by demons (aliens, gods, God, whatever the label shall be, just as long as they evolved over a great period of time like we did) is no less scientific than the act of contemplating the possibility of the many worlds scenario.

            I say this wholeheartedly, because even if one were to somehow logically disprove many worlds here, there is still the possibility that there is another world in which this logic was proven false because it was based on some incomplete information. I also say this wholeheartedly, because the simplest thoughts about the origin of life point directly to the laws of thermodynamics themselves -- life is special, but not that special.

            Anyway, who knows? Perhaps one day we will be able to communicate with aliens, as well as be able to hop between the branches of the many worlds. Until then, my bet is on aliens first, and possibly last.

            Dear Emily,

            You write exceptionally well. You give a balanced and mature analysis that reveals a strong grasp of the issues you address, without being carried away by any particular argument. I have a few thoughts for you to consider.

            1. Of course you are correct that classical microdynamics is time-symmetric, but we know beyond reasonable doubt that classical statistical mechanics is not fundamental. A general mechanism that produces time-like asymmetry across a broad range of "fundamental" physical theories is asymmetry in configuration space. My own favorite version is causal configuration space, as described in my essay:

            On the Foundational Assumptions of Modern Physics

            The idea is that different possible universes are related to each other in ways that make time-like asymmetry inevitable. I say "possible" here because I don't believe one has to be a committed Everettian to make use of configuration spaces and Feynman's sum over histories method. I also explain in the essay precisely what I mean by "time-like" in this context.

            Julian Barbour's essay in this contest mentions a different type of configuration-space asymmetry, shape space asymmetry, which is relevant under different assumptions. He can explain his approach better than I can.

            2. As you point out, there is a self-referential difficulty associated with doubting one's own memory; you mention this by remarking that your essay is "more likely" of random origin than produced by a conscious person. To your credit, the essay itself is strong evidence against this supposition, but more seriously, I believe that the pragmatic assumption you mentioned is necessary, if only as a last resort. There is no incompatibility between pragmatism and idealism in this regard, unless one is certain that one can never do better than the pragmatic assumption. You can continue to do science and seek better foundations at the same time.

            3. On the subject of decoherence, I will mention that Jorge Pullin and Rodolfo Gambini have an essay in this contest that attempts to refine the decoherence approach to the measurement problem. I will also repeat that ascribing some degree of reality to the various histories in Feynman's sum doesn't necessarily imply full-blown Everettianism; in particular the relationship between observers and the configuration space admits several possible interpretations.

            4. Einstein's objection to nonlocality need not have been totally wrongheaded, even if it was misapplied in the case of quantum theory. In particular, it relies on assumptions about the structure of spacetime. I discuss this point in my essay, as well.

            Thanks for the great read! Take care,

            Ben Dribus

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              • Post #17

              Dear Emily,

              i read your essay and i realized that you thought *deeply* about the consistence of our theories with our human experience of time, constancy, space and retrodiction. It was a joy to read your lines of reasoning!

              May i comment that all your questions about the real physical circumstances could be answered by introducing my concept of "physical retrodiction". How this works is outlined in my own essay. You don't need to assume Many Worlds or a universally valid wave function. The wave function only does "collapse", because every measurement is both - an initial state and a final state. These states get rendered permanently to be consistent to each other via entanglement - and this is the reason why it *seems* for us that someting like a wave function does collapse. Its only our biased classical, mechanical view that induces the reasoning about a collapse.

              Thank you again for your very exciting essay!

              Stefan Weckbach

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              • Post #18

              Emily

              You are ignoring my post.

              Why?

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              • Post #19

              Hello! I'm sorry that I took some time to reply, I have been busy.

              I'm sorry, but I don't entirely understand your question - what do you mean by 'victimization' with regard to the second law?

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              • Post #20

              Dear Emily Adlam,

              Didn't they intuitively decide that frequencies have to be positive while they didn't overlook the due consequences? I can provide references that reveal what e.g. Schroedinger, Dirac, and Weyl thought.

              Well, you are not reading mathematics. However, I consider the mathematical flaw related to physics.

              Curious,

              Eckard