Monday, June 10, 2024

Carroll tries to defend Many-Worlds again

Physicis Sean M. Carroll tries to answer this question:
Joel remok says if we can't access any of the many worlds, what 2:31:07 is the purpose of studying it, when there are still many discoveries to be investigated in the reality we exist in?
Good question. There is no point in talking about parallel worlds that we can never see or know anthing about.

The transcript of his answer:

2:31:13 look I've said before I don't care about the other worlds I care about the laws of physics the question is we have 2:31:20 problems with quantum mechanics as it is taught it is not a sensible rigorous coherent Theory. we make things up like 2:31:28 observations and wave function collapse that aren't rigorously defined. many worlds is a well-defined theory that 2:31:37 replaces the ill defined Copenhagen interpretation and lets us actually do science with it. the point of many worlds 2:31:44 is not the other worlds. it's that we've answered the question of what is a measurement, why do you get probability, 2:31:50 and things like that, and equally importantly there's the fact that we don't know the fundamental laws of 2:31:56 physics. we're not done with physics yet we're trying to build better laws of physics and I strongly think that taking 2:32:02 quantum mechanics seriously and thinking about what is the correct foundational version of quantum mechanics will be 2:32:09 useful to that program. so again it's not about the worlds. people who really 2:32:15 obsess about the other worlds are the ones who haven't really internalized many world worlds many worlds is just 2:32:22 it's always obeying the Sher equation that's the essence of the theory
No, this is nonsense on every level.

Many-worlds does not answer the question of what is a measurement. It says that a measurement splits the worlds, but there is no explanation of how the worlds split, how many worlds there are, how you knowt he worlds have split, or anything. It is no better than how bohr explained it.

Many-words says nothing about how we get probabilities. The many-worlds folks do not even believe in probabilities.

Saying that Copenhagen is ill-defined to do science is backwards. Copenhagen has had successes worth trillions of dollars. No one has ever done any science with many-worlds.

I don't know how Carroll says this junk with a straight face. It is like saying Astrology is the only true science.

Here is the distinction. Copenhagen says you can predict an experiment, with probabilities for different outcomes. Once you observet the outcome, you discard the other possibilites as events that did not happen.

Many-worlds is just like that, except that there are no probabilities for the outcomes, because they all happen, and no world is any more likely than any other. Once you see an outcome, the parallel worlds with the other outcomes go out of reach. A prediction might seem true or false, but that is only because you are trapped on one of the worlds. It is not possible to do any science, because no prediction can ever be falsified.

Copenhagen makes sense and is scientific. Many-worlds is an unscientific fantasy.

10 comments:

  1. Copenhagen doesn't make sense, and that's why there are so many silly theories out there. There is no "collapse" but complex nonlinear interacting fields. There are no quantum states or probabilities. You don't need to modify field theory, at least not much, to explain "collapse". People have simply refused to think in detail about how experiments actually happen. Copenhagen is pure mystification. This mystification has led to attempts at modifying the Schrödinger equation or introducing random collapse theories. To say that the wave function is just information is an admission that Copenhagen has given up on providing an ontology for physics. Scientific theories are not about ultimate Truth but better and better versions of false. The positivist position is too extreme in its skepticism. We have a perfectly functioning field ontology. Just look at Chip Sebens' work on spin. We can explain things clearly!

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  2. Copenhagen makes sense and works. If it didn't, then you would not even be able to read this message, because it is transmitted by devices built by people who learned Copenhagen from textbooks and applied it. We have other silly theories because some people have silly philosophical objections. Let me know when any of those other theories is actually used to make a device.

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    1. Copenhagen provides no unique predictive power. The real issue is that Copenhagen utterly fails to provide an coherent physical ontology or account of what the quantum state actually represents in reality. Saying the wave function is just information is a cop-out, not an explanation. Information about what, exactly? Copenhagen is a philosophical dead-end that resorts to irreparable discontinuities and classical/quantum divides (see Yale's Peter Morgan on this point).

      In contrast, the view I advocate is that we take existing quantum field theory seriously as representing real physical fields evolving in space and time according to the field equations. There is no fundamental quantum/classical split - just an extraordinarily rich landscape of nonlinear field dynamics. So-called "quantum phenomena" like superposition and entanglement emerge naturally from this unified field description. Wilczek's Core Theory unification provides a consistent low-energy (IR) effective field theory that accurately describes most observable physics. Field ontology can perfectly well explain spin, entanglement, and all quantum phenomena without contradictions.

      While the predictive mathematical formalisms of quantum theory are wildly successful, the conceptual foundations of Copenhagen are an incoherent dead-end. We must go beyond its subjective divides and radical indeterminacy to a realistic unified field ontology. That is the path forward.

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  3. Roger,
    Epicycles work quite well for quite a bit of astronomical calculations, but,
    As a model, they have nothing to do with how orbits structurally work. Orbits are not perfect celestial circles within circles, that's how a mechanical watch works, not the heavens.

    Chemistry is largely based on the Rutherford model of atomic structure, no one would argue it doesn't do its job well,... for heuristic kludge. However, we have known for a fact for quite some time that atoms aren't structurally anything like the Rutherford model... so studying the model won't really lead to any insights into what is going on in atomic structures. This is why so many rules of thumb and constant retcon patch jobs are required for modern chemistry to function, it isn't an accurate structural model.

    The Copenhagen 'interpretation' is much the same. Just because your algorithm spits out something useful does not mean it is actually modeling (or explaining) how the actual system works, and if you study the model no matter how closely, it will not give you insight into understanding of the reality ... because it isn't the reality, it's a model.

    Ancient Romans believed disease was caused by divine or supernatural sources, but,
    Their solutions were functionally pragmatic in nature (provide clean air, water, regular bathing, and sanitation), and so they largely worked quite well to prevent the spread of contagion and disease. Solutions explanations often aren't why they work.

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    1. I do not agree that "Epicycles ... have nothing to do with how orbits structurally work." Of course they do. The structure of those orbits is described by the epicycles. You can describe them without epicycles, but that epicycle structure is there anyway.
      I also say that Copenhagen does model how actual systems work. People sometimes say otherwise, because it does not explain the hidden variables. But there are no hidden variables, so there is nothing to explain.

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    2. Roger,

      Epicycles don't take into account the nonlinear dynamics.

      While on this topic, shall I expect you to ask your reader and replier "MD Cory" to clarify the place (and it's not "Chip" Sebens' output) from which he got the more specific nonlinear theory for solving the QM Measurement Problem right (the version he mentions), in first instance, if not mine?

      Best,
      --Ajit
      PS: Cory seems known to you. His name and other details aren't available on the 'net, however. Hence the request.

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    3. See the work of Chip Sebens, Peter Morgan, Alexey V. Melkikh, Arnold Neumaier, etc. https://arxiv.org/abs/2109.04412

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