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

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.

Thank you very much for your comments!

1) I've read your essay and Dr Barbour's with interest - if anything, I would say that the points I've raised here give reason to take these sorts of speculations seriously, since the problems with classical statistical mechanics would make it unsatisfactory even if we didn't have other good reasons to view it as non-fundamental.

2) I certainly wouldn't advocate giving up all or even most of the pragmatic assumptions that we need to get physics started. However, I do think we should keep in mind that they are assumptions, and be willing to question them (judiciously) in circumstances where that becomes appropriate, such as our current predicament with regard to statistical mechanics and quantum mechanics.

3) Bringing in alternative interpretations of quantum mechanics certainly complicates the issue here, but I think the problem of probability remains pressing for any interpretation which ascribes reality to more than one outcome of a measurement, since it's then no longer possible to make the straightforward pragmatic assumption that the (single) course of events that actually happens is one rendered highly probable by the theory.

4) I agree - I think there's a prevailing idea that Einstein disliked nonlocality mainly because it disagreed with his own theory of relativity, and that's doing him an injustice, because he clearly had good independent philosophical reasons for opposing it. I think he's right to worry that if we were to get rid of locality altogether we'd simply end up with chaos; but what quantum mechanics demonstrates is that we can sometimes weaken underlying assumptions like locality without completely undermining the practice of physics.

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

Hello Emily,

It seems very strange to argue for the possible unreliability of evidence/memory, by pointing out problems in fields where our knowledge is very limited. Problems will always arise in fields like that anyway. Cosmology is sometimes portayed as a field within which we have a good understanding, but it isn't. We found out in the '90s how little we know.

You can't point out that some things about entropy don't make sense, and then say that this means our memories may be deceiving us somehow. Penrose pointed out some absolutely major problems with entropy in cosmology 30 years ago, and basically said that no-one except him seemed to see these problems. But our idea of entropy may be flawed, or the concept may be limited, or our undertanding of it may be incomplete. There are all kinds of unknowns surrounding these questions - our cosmology may be partly wrong, it's certainly incomplete. That's science, there are things that don't add up, you have to try to solve them. You may be right to re-examine the relationship we have with evidence and memory, but you can't present problems like those with entropy as reason to think this or that in your argument.

Best wishes, Jonathan

Just to put that in a wider context, and explain why to me it seems premature to question the reality of the information we have because of the entropy problem - many areas of physics has had problems that at first seem impossible to deal with. Some people seem to run away from the unsolved puzzles, or try to diminuish their importance.

I'm not saying you do that, but I do think we should take these puzzles on, and be prepared to say 'this is baffling, we don't know what's going on'. In the past, those who have been prepared to look right into the cracks in our picture - like Einstein - have found the best clues waiting there, while others spend their time papering over them. I don't think you do that, but it seems to me there's nothing wrong if we're baffled, puzzles like interpreting QM have an interesting way of ruling out a large range of solutions, leaving us little or nothing that seems to work. That means it's a good puzzle, and that's why we struggle with them! But when a solution appears, it often seems less weird than it looked beforehand. Anyway, that's how I see it.

But also, when you look at the entropy problem, don't forget the possibility that motion through time exists, as George and I both think. (See my essay for evidence and reasoning that suggests it does.) If it did exist somehow, there would surely be some missing pieces of the puzzle still to be found, and that area looks connected with the bit of the puzzle you're looking at. So as I said, there are many unknowns in that area.

I'd like to see more about the mechanism that you think might be making our data contain unsolvable puzzles, if it's there I want to know about it.

Anyway, good luck,

Best wishes, Jonathan

I certainly agree with you that our knowledge is limited in these fields, and indeed, I'd suggest that the problems I point out are one symptom of that fact. My intention is not to use the difficulty with entropy to argue that it must be the case that our memories are deceiving us: rather, the argument is comparable to a reductio ad absurdum, to the effect that our usual scientific practice, applied to the evidence we have, leads us to a theory which apparently tells us we shouldn't rely on that evidence in the first place. As you rightly say, 'there are things which don't add up, you have to try and solve them,' and my suggestion is merely that given this problematic relationship with evidence, perhaps one direction of investigation is to look more carefully about the assumptions we are making about evidence in the construction of our theories. I certainly don't want to suggest this is a problem which is impossible to solve - using your metaphor, I think these difficulties with evidence are among the 'cracks in our picture,' into which we ought to look, as Einstein did, in order to find fruitful directions for future progress. Indeed, I'd say that what Einstein did was very similar to what I'm advocating: by relaxing certain assumptions once thought necessary to the practice of science (in his case, about the nature of space and time), it becomes possible to see issues in a new light and open up new avenues for scientific theorising.

Hello Emily,

Thank you for your reply. I agree that if we have to question evidence or assumptions, it's often better to questions assumptions.

I just reread your essay - to me you show the limitations of certain theories very well, by showing what happens when they're applied outside their domains of validity. One reductio ad absurdam you set out is that according to statistical mechanics your essay was more likely to have arisen by chance than be written. I think one more positive side of your work is that it might contribute to defining the boundaries, as we probably need a more exact understanding of what that sort of physics can and can't describe. To me, having shown these limitations to that sort of physics, it's a pity if you then take the theories as being actually applicable in those domains, as you sometimes seem to.

I'm trying to understand your idea about memory - you say:

"For although the claim that we are at a local minimum of entropy is inconsistent with the history stored in our memories, it is not inconsistent with the existence of those memories - they, together with the order we perceive around us, could have been created by a spontaneous fluctuation rather than by the events they apparently report."

So a random fluctuation might have caused all of our memories, and the order we percieve around us, to come into existence? I just don't understand how so much order, and consistent order - our memories tend to agree on things - could arise from a random fluctuation, whatever one thinks about the way in which memories are stored. Wouldn't a random fluctuation be likely to create something very much more... random? Douglas Adams once described a planet covered entirely with luxery hotels and casinos, that had all been 'carved out of the rock by the natural processes of wind and erosion'. To me, your idea looks a bit like that. Surely the order we find around us is more likely to have appeared in the kind of way we think it did, but with gaps in our knowledge about it.

And where you talk about applying probabilities to the history of the universe - to do that you tend to need to know everything. It seems to me that because we don't, we're not in a position to do that.

I think what I may be seeing underneath your essay is a different version of something I find in many places nowadays - the implicit assumption that we now have all the pieces of the jigsaw in front of us, and only need to arrange them correctly. No-one would actually say that, but people nevertheless think and write as if it were the case. Many people are 'shuffling the principles' at present, making basic principles that were thought to be fundamental become emergent, and vice versa. I've had a discussion with Ben Dribus about this - personally, I think rearranging what we have will not be enough. In my essay, I remind people that there must be missing pieces, and that we need to allow for them, and try to guess - from the clues we do have - what the clues we don't have might look like.

And this principle of 'allowing for unknowns' would be very helpful in your discussion about QM and the Everett interpretation. It seems likely to me, and to many, that the real interpretation of QM is something different from all of our 5 or 6 present alternatives, all of which have their own problems. If so, feeding in what we have now and assuming it's everything will only give nonsense out, which is I think what you do, and what you get. I know you intend to show that many of these avenues of thought simply don't work, and I think you're right, you show that very well - to me only your suggestion about why they don't work is wrong.

Anyway, best wishes, Jonathan

Sorry Emily, just to correct a mistake in the first line above, you were talking about questioning assumptions about evidence, not questioning assumptions.

The crucial point I forgot to make about QM is that the "problematic relationship with evidence" which you claim exists arises largely from a theory that has no clear interpretation, and has simply not been understood. We've also had trouble applying statistical mechanics, and yet you assume we can rely on our understanding of these two theories when you form that initial premiss. JK

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Sergey Fedosin