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We went a little off topic in physics class today and my teacher was explaining how quantum physics explains the idea of parallel universes. She believes in a idea called many world interpretation where the universe consist of timelines that continuously splits leading to an $\infty $ of parallel universes. She says that it is because particles have wave properties and waves can be in two places at once. So all particles appear in multiple places, but in its own universe. I want to know how does physics explain this theory of parallel universes? I understand the timeline concept, but not the physics. Any explanation will be very much appreciated!

If we are made out of particles then we exhibit wavelike characteristics, right? So, then can theoretically(if quantum theory is proven to be true) be an infinite number of particles that are us, just in different parallel universes which we can't observe?

Can anyone explain to me the physics behind this MVI? I will try to follow each and every answer to the best of my ability.

Below is a picture of the timeline! It keeps on splitting and we remain on one, other version of ourself remain on others? :enter image description here

Side Note:I looked at wikipedia, but it only refers to a wave function and doesn't give a concrete understanding

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    $\begingroup$ No real physics in the sense of experimental physics. It's an interpretation of quantum mechanics. I'd suggest to first have a look at what interpretations actually are: physics.stackexchange.com/q/145772 then have a look at the MWI: There are many threads about it here, but I didn't find a low-level intro. Until then, maybe you want to have a look at here kim.øyhus.no/QM_explaining_many-worlds.html. Then also look at criticism physics.stackexchange.com/q/6096 $\endgroup$
    – Martin
    Commented Dec 14, 2015 at 22:37
  • $\begingroup$ @Martin Ok I will look at that right now. $\endgroup$
    – James Smith
    Commented Dec 14, 2015 at 22:43
  • $\begingroup$ WHY THE DISLIKE? It was an honest question? There probably was a lot of premises that led to Many-World Theory. And I just wanted to understand them. $\endgroup$
    – James Smith
    Commented Dec 14, 2015 at 22:49
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    $\begingroup$ James, it wasn't me who downvoted you. But I have to say this : the many-worlds multiverse is wondrous fantastical "woo". It's popscience nonsense that's been peddled by quacks and charlatans for fifty years. There's not a shred of supporting evidence for it, and it tramples all over things like conservation of energy and causality. How exactly does the universe split into two every time I hesitate about having sausage sarnies or bacon baps? It doesn't, because the MWI is trash. Physics doesn't explain it, and it explains nothing. Your teacher is behaving irresponsibly I'm afraid. Sorry. $\endgroup$
    – John Duffield
    Commented Dec 14, 2015 at 23:07
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    $\begingroup$ John Duffied: About evidence for many worlds. I believe that universe has a single wavefunction, and this is the reality. There are no 'branching points' as is often described by many-world interpretation, but there is decoherence as usual from which classical reality emerges. This is absolutely the simplest explanation and should be accepted by Occhams razor until better ones are available. Instead, there is absolutely no evidence of any wave function collapse by a measurement without involving environment states, the proof burden is on the more complex interpretations I believe. $\endgroup$
    – Mikael Kuisma
    Commented Dec 15, 2015 at 0:18

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You essentially answered the question yourself when you said it is because quantum particles are waves and can be in more than one place at once. The physics, or mathematics of this is the mathematics of waves, superposition, linear algebra. It's essentially quantum mechanics. So study quantum mechanics. I understand the literature on quantum mechanics isn't exactly enlightening. It requires deep thought. I'm working on presenting these sort of ideas in a more intuitive way. However for the time being, I suggest to learn more quantum theory if you are mathematically inclined. If not, then you'll have to wait.

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As far as I know the parallel universe (or multiverse) theory has two reasoning:

1- How can we get rid of the idea of god?
In the universe we live, the physical laws seems as if they are fine tuned for the form of life we know to exist. Of course this cannot be true!!! Therefore there must be some other (infinitely many, to be precise) universes with, say, gravitational constants varying all over the place where primates could never stand up, etc.

2- How can we make sense of the measurement problem and probalistic nature of quantum mechanics?
The best example is the most famous cat on the planet. Until the box is open the cat is both dead and alive (technically speaking in a state with 50% chance of being dead and 50% alive). When we open the box we find the cat, say, dead in our universe. There is a possibility that the cat is alive in another universe.

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  • $\begingroup$ I guess it is a metaphysical question. I thought there would be a lot of physics to support the idea and not just that we don't want to believe in God. I am not going to get into religion because that is subjective. Also for the cat being dead and alive, I don't see how that is possible without parallel universes. It would be dead in one and alive in the other. I don't get what you mean the cat is both dead and alive! That is unless you are talking of two DIFFERENT versions of the cat in there own universe. $\endgroup$
    – James Smith
    Commented Dec 14, 2015 at 22:47
  • $\begingroup$ I have chaned the second point a bit. I hope it is more clear. $\endgroup$
    – physicopath
    Commented Dec 14, 2015 at 22:56
  • $\begingroup$ Yes it is more clear. I don't get why there are so many down votes. For your answer and for my question. I thought it was a pretty interesting question to think about. And I am sure many physicist have asked similar questions to come up with this theory. $\endgroup$
    – James Smith
    Commented Dec 14, 2015 at 22:59
  • $\begingroup$ Because neither the answer nor the question can be written down as an equation. Most of the people think that real physics can only be done through math. $\endgroup$
    – physicopath
    Commented Dec 14, 2015 at 23:03
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    $\begingroup$ "Most of the people think that real physics can only be done through math": every physicist out there thinks that, ergo it is true (as Physics is what physicists do, by definition) $\endgroup$
    – AccidentalFourierTransform
    Commented Dec 14, 2015 at 23:16

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