Underlying Assumptions in Physics: The Relationship Between Evidence and Theory by Emily Christine Adlam

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

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

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

Emily

You are ignoring my post.

Why?

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?

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

Drew attention to quote from Dirac in my essay:

"It seems very likely that sometime in the future there will be an improved quantum mechanics, which will include a return to the causation and which justify the view of Einstein. But such a return to the causality may be possible only at the cost of failure of some other fundamental ideas, which we now accept undoubtedly. If we are going to restore causality, we shall have to pay for it and now we can only guess what idea must be sacrificed." P.A.M. Dirac. Directions in Physics

I mean to sacrifce second law of thermodynamics

Victimization of second law....

I agree that great care needs to be taken with the second law - in particular, I would reinforce that it shouldn't be taken as a 'fundamental' law (whatever that means!) but rather as a statistical generalisation which holds as a matter of high probability.

I invoked entropy in this essay mainly as a simple way of pointing out the asymmetry that exists between our predictions and retrodictions - the problem is that if we accept the time-symmetry of the microdynamical laws we seem to have no good reason not to believe that the 'entropy' (using this concept as a way of formalising closeness to thermal equilibrium, without presupposing any substantive claims about irreversibility or the second law) should increase in both the past and future direction. Only the past hypothesis gives us an adequate basis for retrodicting lower 'entropy' states in our past, yet our principal reason for accepting the past hypothesis is our belief that entropy was in fact lower in the past - hence we seem to have a circularity in our reasoning, and I don't think that alternative definitions of entropy or revisions of the status of the second law will do enough to make the problem go away.

Emily,

One way to resolve the Everett hypothesis is to eliminate the external timeline of events and allow the process to proceed atemporally. Sound impossible? How can you have process without time? It emerges from the process, but it's dynamic, not dimensional. It's not the past proceeding into the future, but the future becoming the past. Not the earth traveling a narrative dimension from yesterday to tomorrow, but tomorrow becoming yesterday because the earth rotates. As an effect of action, time then becomes the collapse of probabilities into actualities. Duration is not external to the present, but is the state of the present between measured events. It is only when we consider time in retrospect that it emerges as narrative. Yet that past is receding, rather then the present moving.

As an effect of action, time is similar to temperature. Time as rate of change, while temperature as level of activity. When we change the level of activity, such as in gravity fields, or at significant speed, this affects the rate of change. Which is why clock rates vary. Not because they travel alternate time vectors.

This way, the past is determined, but the future is probabilistic, since the lightcone of input is not complete until the event happens.

EA:

Very interesting and informative essay as philosophy.. As a newcomer to the FQXi community, I feel few of the "community" grade, or even look at, my essay which approaches the problem very realistically, based on an internal philosophical view.. Might you look at it, comment if so inclined, and grade it?

To Seek Unknown Shores

聽聽 http://fqxi.org/community/forum/topic/1409

Thank you

TE

You needn't hurry. However, I would like to eventually get an answer. Aren't all my five Figs. clearly understandable as seriously challenging key tenets as solicited with the topic of this contest?

Eckard

You didn't see contradiction?

Temporal asymmetric symmetry..or symmetric asymmetry.

Emily

Have you considered entropy with respect to a cyclic universe model? Perhaps consider a larger model of an AGN accreting and re-ionizing all the matter in the disk as quasar jets (or any other you may prefer). To me this would demand a re-evaluation of the assumption or concept of entropy. Do you?

I also wonder, considering the evidence, if it really is the case that;

"we have in fact been able to construct a coherent and successful quantum theory which violates locality, and its laws certainly seem susceptible to empirical test." Do the 'empirical tests' really tell us that or is it just our interpretation, as I suspect?

A well written essay no less, and an easier read than some. That possibly includes mine, which I do hope you'll read anyway. It does add some theatre to a very intense mechanistic analysis which addresses some of the questions you raise and offers some logical mechanistic solutions. I'd value your thoughts.

Many thanks, and well done.

Peter

I do also have an interest in Special Relativity, but in this essay I chose to focus on other issues in foundational physics. Special Relativity does face certain problems concerning the nature of the evidence for it, but I don't think it's subject to the kind of 'reductio' difficulty that I'm considering here, where the theory itself seems to prompt us to conclude that we shouldn't trust the evidence for the theory.

The evidential status of Einstein's light postulate is interesting. It rather looks as if Einstein's approach was based more on intuition than on empirical evidence. However, I think we can still separate the context of discovery from the context of justification and ask what evidence there is now for the light postulate, whether or not Einstein himself took that evidence into account.

You could consider special relativity as representing an antithesis to your thesis in the essay. You wrote:

"Special Relativity does face certain problems concerning the nature of the evidence for it, but I don't think it's subject to the kind of 'reductio' difficulty that I'm considering here, where the theory itself seems to prompt us to conclude that we shouldn't trust the evidence for the theory. The evidential status of Einstein's light postulate is interesting. It rather looks as if Einstein's approach was based more on intuition than on empirical evidence."

There was no evidence for the constant speed of light in 1887 - rather, the null result of the Michelson-Morley experiment was in fact counterevidence:

John Norton: "In addition to his work as editor of the Einstein papers in finding source material, Stachel assembled the many small clues that reveal Einstein's serious consideration of an emission theory of light; and he gave us the crucial insight that Einstein regarded the Michelson-Morley experiment as evidence for the principle of relativity, whereas later writers almost universally use it as support for the light postulate of special relativity. Even today, this point needs emphasis. The Michelson-Morley experiment is fully compatible with an emission theory of light that CONTRADICTS THE LIGHT POSTULATE."

Eventually the theory itself prompted its supporters ("later writers", as John Norton calls them) to believe and teach that the counterevidence was in fact glorious confirming evidence:

Faster Than the Speed of Light, Joao Magueijo: "A missile fired from a plane moves faster than one fired from the ground because the plane's speed adds to the missile's speed. If I throw something forward on a moving train, its speed with respect to the platform is the speed of that object plus that of the train. You might think that the same should happen to light: Light flashed from a train should travel faster. However, what the Michelson-Morley experiments showed was that this was not the case: Light always moves stubbornly at the same speed. This means that if I take a light ray and ask several observers moving with respect to each other to measure the speed of this light ray, they will all agree on the same apparent speed!"

Marc Lachièze-Rey: "Mais au cours du XIXe siècle, diverses expériences, et notamment celle de Michelson et Morley, ont convaincu les physiciens que la vitesse de la lumière dans le vide est invariante. En particulier, la vitesse de la lumière ne s'ajoute ni ne se retranche à celle de sa source si celle-ci est en mouvement."

Stephen Hawking: "So if you were traveling in the same direction as the light, you would expect that its speed would appear to be lower, and if you were traveling in the opposite direction to the light, that its speed would appear to be higher. Yet a series of experiments failed to find any evidence for differences in speed due to motion through the ether. The most careful and accurate of these experiments was carried out by Albert Michelson and Edward Morley at the Case Institute in Cleveland, Ohio, in 1887......It was as if light always traveled at the same speed relative to you, no matter how you were moving."

Pentcho Valev

Emily,

Thanks. I agree, but suggest that if a consistent interpretation exists that DOES allow local reality and derive the effects of classical physics, then it would be a unifying theory. The test may be it's effectiveness in resolving anomalies.

I suggest that because I seem to have chanced across such an ontological construction, built from many epistemological elements, to bridge the divide. I hope you may do a careful read of my essay assembling those parts with dynamic logic foundation, and let me know where it is I went wrong.

Many thanks.

Peter