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Thread: many worlds vs sliding doors: a (partial) explanation of quantum woo?

  1. #1
    Join Date
    Apr 2010

    many worlds vs sliding doors: a (partial) explanation of quantum woo?

    Is it true that in the 'many worlds' interpretation of quantum mechanics- that the universe only splits when a quantum measurement is made....

    So that when we talk about macroscopic objects like Gwyneth Paltrow's brain and the sliding doors of the train in the the movie 'sliding doors'.... because they have already decohered, there is no split?

    ..but IF she had used the "Universe Splitter" app to decide whether to takes the train or not... the universe would have split?

    .. and do you think this confusion has contributed to a lot of 'quantum woo'?.

    Helen Quilley (Gwyneth Paltrow) gets fired from her public relations job. As she leaves the office building, she drops an earring in the lift and a man picks it up for her. She rushes for her train on the London Underground but just misses it as the train doors close; but the film then rewinds and the scene is replayed, except that now she just manages to board the train. The film continues, alternating between the two storylines in which different events ensue (but with occasional intersections of the two).
    "It's only a model....?" :-)

  2. #2
    Join Date
    Aug 2013
    Quote Originally Posted by plant View Post
    Is it true that in the 'many worlds' interpretation of quantum mechanics- that the universe only splits when a quantum measurement is made....
    If it is watch out for the 'wobble bug'.

    In the late 1990's, when dual processor computer motherboards became available, a problem was slowly brewing with regards to poor software programming techniques. This problem would pop up its ugly head in the MS COM+ model when the (usually MS VS) software declared a global variable and later on changed the type of that variable. In these cases dual cpu systems with multiple threads per core would just start up another duplicate thread and continue processing, a 'split' if you like.

    The problem was that the system only had a maximum of 8 threads available so when a global variables type had been changed for the 8th time the entire application fell over in a screaming heap after losing overall processing power on each split.


  3. #3
    Join Date
    Jul 2005
    I think you'd need to define what you mean by "quantum woo", since that can cover a lot of ground.

    But I don't think decoherence does anything to avoid the probabilistic split in the many-worlds interpretation - it converts a superposition to a set of classical probabilities, and how Nature chooses which probability we experience (the "measurement problem") is the point at which MWI comes in.
    So if you believe (as some people do) that free will derives from neuronal structures in quantum superposition, then decoherence is what makes us act on either one decision or the opposite, at which point we can invoke Many Worlds if we're that way inclined. I personally don't recognize that sort of random "free will" as being the sort of free will people claim to have, but decoherence certainly doesn't seem to stop QM probabilities from playing themselves out in the classical world.

    Grant Hutchison

  4. #4
    Join Date
    Sep 2003
    The beautiful north coast (Ohio)
    Quote Originally Posted by plant View Post
    So that when we talk about macroscopic objects like Gwyneth Paltrow's brain
    As best as I can tell, there is no evidence for this object....
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

  5. #5
    Join Date
    Oct 2005
    The core idea behind the MWI is that everything evolves via the Schroedinger equation, and that's it. By "everything", I mean "the universal wave function", so there is the implicit (and quite important) assumption that there is such a thing as a universal wave function. The wave function never splits, and all that is meant by "classical scale" vs. "quantum scale" components is how complicated are the entanglements. Decoherence is when the entanglements become so complicated that correlations start breaking down into very sparse islands. You might picture it as what happens when you pour water over a windshield: as the water depth falls below a critical level the smooth water surface breaks up into tiny droplets, where you think of the droplets as regions in the universal wave function that maintain some degree of mutual quantum coherence, while separate droplets have no surviving cross-correlations. What you end up with is still just water on the windshield, but each droplet has achieved a kind of separate identity-- that's the "splitting" of the "many worlds."

    Now when we consider our perceptions, and why we never perceive anything like the universal wave function but instead only perceive "one droplet" of the whole, there has to be a kind of interface between the universal wave function and the way humans interpret and process information. If you don't say anything about human minds, the MWI proponent would say that the whole reality is all the many uncorrelated droplets that appear from the straightforward application of the Schroedinger equation under "decohering" conditions (which is the natural way that equation works when there is lots of complexity of interactions). If you then bring in the human perceiver, you would say there are perceptive agents in every one of those droplets, each wondering why they got that particular set of outcomes instead of any of the others, seemingly at random. From the MWI perspective, nothing random is happening, every droplet is just wondering why their outcomes seem random to them but all the outcomes have occurred. If you now imagine a single conscious thread passing through a chain of these droplets as they evolve in time (say, with more rain being added and new droplets forming), the conscious mind can again ask itself in a time-evolving way why it got these outcomes, be they lucky or unlucky, and not some others. But the question is essentially meaningless from the MWI perspective-- yours is simply the consciousness that exists in that internally coherent set of outcomes, that's what you mean by "you"-- so you may as well ask why you have your DNA and not mine. (And note you can't say you have your DNA because you have your biological parents, because then I'll just ask why you have your parents and not mine!)

    Then of course we can look at how free will appears in the MWI perspective. Here there are several possibilities that would all be consistent with MWI and require a better understanding of conscious identity. One way to go would be to say that if different droplets appear at the end of different free-will choices, we still have all the droplets populated by consciousnesses that track back their own history in a similar way except for that last choice made, and the similar consciousnesses then have to "after the fact" create a kind of illusion that that consciousness made that choice and had that effect, whereas all that really happened is that consciousness is now defined by being the one associated with that choice. This approach would be like saying that consciousness is not a kind of conscious entity that flows through time, it is more like a sequence of outcomes, like if you look at a photo of a river and say that there is water in each branch of a delta but it's all the same water from your point of view.

    Another approach would be to look at individual water molecules and imagine each is a distinguishable entity following the branches of a river delta, so that there really is a continuous path taken by a single molecule/consciousness. If you take that picture, you can say that each individual consciousness "chooses" its own path based on some kind of agency that consciousnesses have (that water molecules don't), so the consciousness is not defined by its choices, it is defined by its identity and it actually makes choices for its path. You could also take a kind of hybrid scheme where the consciousnesses are individual and separate entities that exist continuously through time but don't make choices, they only choose to interpret their path as if they made the choice to go that way-- but if one would take that perspective, I see no reason why you'd even give the consciousnesses separate identities, you may as well just say (as in the first approach above) that the consciousnesses just are, and each creates its own sense of being based on the branch that it is already on. That would be like saying a water molecule does not have an identity which then takes a given path, its identity is defined by the path it takes (which is the way water molecules would actually be treated in quantum mechanics).

    Bottom line: the MWI is what you get when you choose to interpret everything from a very literal application of the way quantum mechanics works. To give it great significance pretty much requires that you don't think humanity will ever come up with a superior and completely different model, or even, perish the thought, you think the universe actually uses quantum mechanics to decide what happens (which from my way of thinking would be tantamount to admitting that you think the universe is really a simulation of some kind, and you have intuited its programming.)
    Last edited by Ken G; 2019-Sep-27 at 09:54 PM.

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