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My understanding of QM is only surface-level, so there may be subtleties I'm missing, but this presentation's arguments against the many-worlds interpretation s
by AgentME 9y ago
My understanding of QM is only surface-level, so there may be subtleties I'm missing, but this presentation's arguments against the many-worlds interpretation seem pretty weak.
Page 28 grudgingly alludes to the idea that MWI could be simpler than other theories ("Objection based on surprisingly common misconception that standard QM defined solely by Schrödinger's equation ... It is only within a many-worlds framework that this view could begin to make sense"), but later introduces MWI as a contender beginning with a nonsense news headline and then characterizes it as intuitively bizarre for proposing a large multiverse, as if the size for its proposed multiverse was an obvious point against it. It seems to me there's an implied misuse of Occam's razor: "Entities are not to be multiplied without necessity" is most properly applied to the number of rules in a theory, not the amount of matter a theory predicts. (If you apply it based on the amount of matter a theory predicts, then Occam's razor surely should rule out theories that dim clusters of light in the sky correspond to trillions of galaxies like our own, and should prefer theories that predict that they're illusions, reflections, or something otherwise insignificant that fits the observations.)
Page 39 and 40 both quote paragraphs from books that seem more convincing to me than the presentation's seemingly hand-waving refutations. Page 40's refutation appears to do nothing but insist upon PWT's "epiphenomenal 'pointer'", naming our branch as real and explaining away the many deep interactions of other branches as only being "mathematical significant" rather than having "ontological significance". ... Maybe this is a bad time to mention my preference for the Mathematical universe hypothesis ("which posits that all computable mathematical structures (in Gödel's sense) exist"), which seems to make the idea of something having mathematical significance but not ontological significance meaningless.
- colordrops 9y agoOccam's razor is so commonly misused and abused. It seems to be more often used to support whatever pet theory someone has rather than as an impartial tool.
- millstone 9y agoThe "nonsense news headline" and followup discussion are less critiquing MWI than poking fun at David Deutsch. This is because Deutsch is a prominent critic of PWT. The arguments against MWI from Occam's Razor are indeed weak. The stronger critiques are the difficulty of deriving the Born rule, or indeed quantum randomness at all, from the deterministic MWI. This is presumably what the authors hint at in their "doubtful it [pure Hamiltonian evolution] makes sense even there (in MWI)".
- AgentME 9y agoWhy do you say that quantum randomness is a problem in MWI? I thought it was one of the neat things of MWI that it doesn't require randomness. There are no random events: instead you have a branch for each outcome. The only randomness is which branch you find yourself in as an individual.
- XorNot 9y agoIt's a problem because it closes off further investigation - same as the anthropic principle. It's an answer for everything, but doesn't tell us anything about where to look next. So if it's right, it needs to rigourously exclude everything else.
- szemet 9y agoOn the other hand objective randomness is a black box. You can describe how it behaves at the surface level (so functionally it is usable), but by definition you can't have a finite model of it, so what is inside? No answer by definition - something infinite. So why X happens instead of Y? 1. Let's propose an unexplainable, unmodellable infinite entropy source under everything vs. 2. X happens and so do Y, and one is observed at a certain probability due to anthropic principle - like this: https://www.youtube.com/watch?v=9R5OWh7luL4 https://www.youtube.com/watch?v=9R5OWh7luL4 The first is somehow psychologically less satisfying answer for me, although - of course - I accept that calculation works either way. The second at least not an unimaginable infinite, and in the end leaves me with less "why?".
- AgentME 9y agoMWI doesn't mean anything and everything can happen because there's infinite universes. The equations of quantum mechanics describe the ways that worlds can branch apart and the proportions of those branches. Sorry if I'm underestimating your familiarity with MWI here; if I am, szemet has a much better response. I'm just a little concerned that some people in the thread don't realize MWI refers to something much more specific and grounded than what-if-multiple-universes, and I wanted to dispel that notion.