Many-world interpretation: simple physics explanation?

Question

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? :

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

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: http://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 http://kim.øyhus.no/QM_explaining_many-worlds.html. Then also look at criticism http://physics.stackexchange.com/q/6096/ — Martin, Dec 14 '15 at 22:37
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. — James Smith, Dec 14 '15 at 22:49
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. — John Duffield, Dec 14 '15 at 23:07
@James Smith: What is your definition of many-world theory? Did you mean many-worlds interpretation (MWI)? — Qmechanic, Dec 14 '15 at 23:15
@JohnDuffield Oh, I understand now. I was under the impression that MWI was strongly supported by members of the physics community. Just like Newtons theory of every force having an equal force with an opposite direction is strongly supported. I guess MWI is more of a belief than physics related. I read an article saying that there isn't any quantitative observation of MWI actually being true. Most of the arguments seem to be you can't prove it false. Anyway, I guess the main thing to get out of this is MWI is just an idea believed by a few and isn't heavily backed up! — James Smith, Dec 14 '15 at 23:16
@Qmechanic Yes I meant many-world interpretation, my teacher referred to it as many-world theory so that was was I thought it was called. But I know better now. Sorry if this wasn't physics related. I thought this was more physics related and there were concrete equations and stuff supporting it — James Smith, Dec 14 '15 at 23:18
@qmechanic I just did, but I guess this post might as well be closed now. I guess I can say I learned what I needed to learn. I was just interested in the physics behind it, but its more of a belief than it is strong concrete physics. The Universe is full of fundamental rules, we observe this rules and formulate ideas. Sometimes these ideas are strongly backed up by math and physics and it becomes part of physics other times these ideas can't be proven. Therefore they remain just ideas that are neat to think about. That what MWI is. It is nice to think about, but we can't prove it. — James Smith, Dec 14 '15 at 23:29
@JamesSmith: I thought that you had a misconception about what Everett's ideas are attacking. That's why I posted the links - and I'm glad to hear that they (among others) helped! Actually, I think it might be worthwile to have a "layman question" about what the MWI is or is not - but I suspect this actually exists and I only found other introductory questions... I don't want to answer, since my understanding is limited, too... — Martin, Dec 14 '15 at 23:32
Please do not take John Duffield's passionately held viewpoint as representative of "the physics community". — WillO, Dec 15 '15 at 00:09
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. — Mikael Kuisma, Dec 15 '15 at 00:18
Good stuff James, you've got it. @ Mikael Kuisma : IMHO you should check out weak measurement work by Aephraim Steinberg et al and by Jeff Lundeen et al, see this: "So what does this mean? We hope that the scientific community can now improve upon the Copenhagen Interpretation, and redefine the wavefunction so that it is no longer just a mathematical tool, but rather something that can be directly measured in the laboratory". @Benito Ciaro : your comment noted! — John Duffield, Dec 15 '15 at 08:21

Marcus Quinn Rodriguez Tenes · Accepted Answer · 2015-12-15T00:16:01.427

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.

physicopath · Answer 2 · 2015-12-14T22:55:29.910

-1

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.

edited Dec 14 '15 at 22:55

answered Dec 14 '15 at 22:40

physicopath

2,352

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. – James Smith Dec 14 '15 at 22:47
I have chaned the second point a bit. I hope it is more clear. – physicopath Dec 14 '15 at 22:56
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. – James Smith Dec 14 '15 at 22:59
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. – physicopath Dec 14 '15 at 23:03
1

"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) – AccidentalFourierTransform Dec 14 '15 at 23:16
Yes, accidently. – physicopath Dec 14 '15 at 23:28
While the second aspect goes in the right direction (although there is not "a possibility that the cat is alive in another universe", but certainty), the first idea is wrong: It has nothing to do with the idea of "god", it is not the many world interpretation (which is an interpretation of qm), but a consequence of other theories trying to extend real physics beyond the standard model. – Martin Dec 14 '15 at 23:28
Fast forward the video to 2:25 and hear the first point from Susskind. Shall we blame the wine? https://youtube.com/watch?v=kpJ51h7bi8g – physicopath Dec 14 '15 at 23:39

Many-world interpretation: simple physics explanation?

2 Answers2