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I was reading about the MWI and how there would be vastly different versions of "you" in the different branches.

I'm just wondering, though, which quantum events lead to such different outcomes? Whether an electron spins left in one universe and right in another doesn't seem like it would lead to significantly different outcomes for me. Particularly as the quantum butterfly effect doesn't exist.

So, I'm wondering which events in our macro world are significantly impacted by macro events such that one world would be vastly different to another.

Quantum Mechanic
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Raheemsterling
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2 Answers2

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That phys.org press release seems to refer to this paper (arXiv).

Quantum mechanics is linear at the level of Schrödinger evolution, and linear systems can't be chaotic. Classical mechanics is also linear at the analogous "level" of probability distributions. But quantum mechanics is nonlinear and chaotic at the level of ordinary particle dynamics, just like classical mechanics. It makes little sense to apply the term "quantum butterfly effect" to an effect that doesn't exist, when there is a real butterfly effect in a quantum world.

It seems very likely that every deviation from perfect homogeneity and isotropy in the universe is due to amplified quantum fluctuations. (That's true in inflationary cosmology, and I'd expect it to be true in practically any alternative to it.) For example, the shape of Earth's land masses was probably determined by quantum fluctuations, and has had an enormous influence on human history.

benrg
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There are lots of things that are improbable, but in MWI are certain to occur in some "branches". E.g. all nuclear plants stop working at any time for any period of time cause all "random" chain reactions stop happening. In some humanity survive "intact" events of trying to start nuclear war for the same reason. Or people (any set of them, and other animals) go blind cause none of photons will interact with retina receptors at that specific entanglement (aka branch). The Sun go black. Etc.

I think there more "positive" outcomes out there too, thought I'm not so sure about below, like iron turn into gold or a person starting to experience euphoria forever.

Martian2020
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