Talk:Many-worlds interpretation

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Branching vs Diverging[edit]

In recent years there has arisen a debate as to whether the 'worlds' branch or diverge. Ever since Everett introduced the term "branching" and DeWitt followed up with "splitting", almost all the litterature on Everettian QM has used the same terminology. However in the formalism of QM, there is noting that indicates that worlds branch, a more coherent view is that all worlds exist and are qualitatively identical up to a certain point and there they diverge.

As the notion of uncertainty has been under attack in the branching view, quite a few proponents of EQM have abandoned it, for instance Steven Weinberg and some others have adopted new views, for instance David Deutsch has proposed "fungible" worlds. Alastair Wilson and Simon Saunders has advocated for the divergent view in the last 4 years in a series of papers. 2 of Wilson's papers here: and Simon Saunders has a chapter dedicated to this in the 2010 oxford volume. — Preceding unsigned comment added by Quantumental (talkcontribs) 15:14, 29 April 2012 (UTC)

- I take the branching vs divergence issue to be an important one, and would welcome an addition to the MWI entry mentioning it. Is the appropriate metaphor for MWI 'parallel worlds' or 'splitting worlds'? It has to be one or the other! Modalizer (talk) 15:51, 22 June 2012 (UTC)

Hawking tacitly accepts MWI as the straight forward interpretation of QM. When asked if the universe is deterministic, he replied, "There are many parallel worlds. In one of those world's Hitler may have won WWII. But since we don't know our future, for all practical purposes we live our lives as if universe were not deterministic." Without interpretation, theories in physics are meaningless symbols. Wheeler and Penrose claimed they rejected the MWI because it carries too much metaphysical baggage. Since when did carrying too much metaphysical baggage become a valid objection to a scientific theory. That is the very same objection raised by the Roman Catholic Church to discredit Galileo's claim that the sun is the center of our solar system. Does the MWI of QM really carry more metaphysical baggage than SR, GR, and the Coppenhagen version of QM? How do you measure just how much metaphysical baggage a physics theory carries before you deem it not valid because it carries too much metaphysical baggage? The article fails to mention that the MWI justifies the anthropic principle, and eliminates the need for the silly concept of complimentarity. Another advantage is it gives a realist view of the universe between measurements. Finally, the Capornican principle favors the MWI. The worlds we can't observe directly are the same as the inside of black hole, or seconds after the Big Bang. Since we will never be able to see the inside of a black hole, or go back in time to Big Bang, we can say whatever physics says about the inside of black holes or the Big Bang is not falsifiable. The distant past, the other side of an event horizon is off limits just like other worlds in Hugh Everett's MWI. ~~ — Preceding unsigned comment added by (talk) 11:07, 15 August 2012 (UTC)

I have an argument in favour of branching over diverging.

Branching or splitting requires the creation of energy, BUT the CoE is not assured to apply outside of each universe.

But if all universes already exist and only diverge, then we must eventually bump into a failure of quantum physics if times goes on as more and more universes are required.

And diverging really requires that existence started off with an exact and limited number of universe's, once things diverge too much we run out of other universes that share a common history.

Additionally some improbably world lines that have longshots occur would run out of common history universes very fast, if something happened with a very long shot of occurring rather few universes would end up with that fate, and even fewer of that same longshot happening again.

Such an outlier universe could run out of neighbouring universes very quickly.

Indeed a universe (or multi-verse) doomsday machine could be built that would create lots of quantum events with millions or billions of outcomes every second, this could potentially exhaust a universe of universes with which to interfere with causing the collapse of quantum physics and presumably the end of too many processes for existence to carry on in that or any other universe that ran the machine long enough. — Preceding unsigned comment added by (talk) 05:10, 23 January 2014 (UTC)

"all possible alternative histories" is imprecise[edit]

In the intro, the phrase, "Many-worlds implies that all possible alternative histories and futures are real," is used. This phrase lacks precision because it fails to define "possible". Looking at particles, for example, a branch point might be a radioactive decay. There might be a very small probability of a given atom decaying, producing two possible outcomes: decay or not decay. However, though it is certainly possible for there to be no nucleus, there is no branch available that would lead to the nucleus simply disappearing. To resolve this ambiguity, I would suggest, "Many-worlds implies that all possible chains of dependent events do play out, creating an extremely large number of alternative histories and futures, all of which are real." -Miskaton (talk) 18:32, 10 July 2013 (UTC)

Hello, Miskaton. The majority of the sources I have read about the many-worlds interpretation describe it very similarly to the way the current sentence, the one you dispute, does. For example, this source by MIT Technology Review (the website) states, "The many worlds interpretation of quantum mechanics is the idea that all possible alternate histories of the universe actually exist. At every point in time, the universe splits into a multitude of existences in which every possible outcome of each quantum process actually happens."
Also, with regard to this edit you made about "cannot" vs. "do not," many sources state "cannot" as well with regard to the many-worlds interpretation. They state this because, as you may know, quantum decoherence makes certain that the different outcomes have no interaction with each other; in fact, various sources state that once the subjects (I'll call them subjects in this case) are decoherent, they can never interact.
I'm not sure about changing the "Many-worlds implies" sentence to what you suggest, and I will wait a week or so to see if anyone else comments on that matter and/or the "cannot" vs. "do not" matter. I suggest "a week or so" because this article is not high-traffic with regard to editors editing it or its talk page. I'm also busy with other matters on and off Wikipedia. So don't think that I'm ignoring you if I don't reply to your followup comment before a week goes by. Flyer22 (talk) 19:15, 10 July 2013 (UTC)
I've come back to this discussion to state that I have not made an additional reply in it because you have not yet replied again, and no else has yet commented on the matters. Flyer22 (talk) 17:09, 1 August 2013 (UTC)

Raub's mysterious poll[edit]

There is enough doubt about Raub's poll that the article (currently) says that "The poll is controversial."

However, I would like to spell out just how dubious this poll is.

First, the only and original citation of the poll that I can find, is in the 1995 book The Physics of Immortality by Frank Tipler, pages 170-171. In the notes it is cited as "Raub 1991 (unpublished)", and there is no entry for Raub in the bibliography, so presumably this is a personal communication.

The Wikipedia article on MWI currently cites, as its source of information about the poll, an obscure recent (2008) book called "The Universe - Solved!"[1], which promotes the idea that we are living in a computer simulation, and an "unauthorized guide" to What the Bleep Do We Know. The latter says the poll was published in "Sciences et Avenir" in January 1998. I have not located a copy of the journal, but this "fact" is also widely cited on the web, saying that Raub's survey was conducted in 1995 and that almost 60% of those surveyed endorsed MWI. Tipler's book was published in 1995, and Raub's survey then claimed 58% endorsement, so most likely "Sciences et Avenir" had an article which mentioned Tipler's book, and this has been garbled into the false claim that Raub's survey was "conducted... in 1995".

Tipler lists Feynman, Gell-Mann, and Hawking as among those who agree with MWI. Feynman died in 1988, so no-one ever had a chance to ask him for clarification. But did he ever verifiably say that he agrees with Everett? Can anyone produce a source for this, other than Raub? Feynman did invent the path integral or sum over histories formalism for quantum mechanics, and since we do not have access to any facts about how Raub conducted his poll, it is possible that he asked his respondents whether this is the most fundamental formulation of QM. But agreeing with that is not the same thing as agreeing with the existence of parallel worlds. For example, Gell-Mann recently coauthored a paper[2] employing a many-histories formalism but arguing for "one 'real' history".

So I think it is fair to say that Raub's poll is not a credible source. It has apparently never been published; the only place where its results are directly reported is a work of many-worlds theology; we know nothing about how the poll was conducted; and its results are at odds with a number of other surveys. Independently of this, we can also say that the current sources for the survey, cited in the article, are not original sources, they are fringe publications even more dubious than Tipler's, and they are just repeating confused claims that they have heard somewhere else.

Perhaps it is reasonable to say that Raub's poll is widely cited on the web, but it's not just "controversial", it is unpublished, unverifiable, and cited only by fringe sources.

P.S. There is an earlier discussion of the poll in "Archive 5". Mporter (talk) 06:50, 2 August 2013 (UTC)

How is "world" defined in MWI?[edit]

I always wondered how the MWI defines a "world". I can't seem to get this knowledge out of the article. Yeah, you can write down Schrödinger's equation and explain the possible states that a state can collapse to with the sentence "all of these states are in another world". But this does not explain what a "world" is.

So, how exactly does MWI define a "world"? What exactly is it that exists after "splitting up"? --2003:63:2F5A:1600:8C0A:C643:6701:12CA (talk) 10:07, 19 February 2014 (UTC)

The Veilerian approach[edit]

the many worlds interpretation is not a testable realistic view but an artistic one, there is one optimum path. We know that because if we measure a spin and then remeasure it, it remains the same. So eternaly a spin is the same, and we might read it as different only is we twist at an angle our detector at a second measurement, or if we do not twist at all the spin detector but if we move it at a close fragment of the light speed faster than the first measurement.

The modern view is that we shape the spin during measurement, and we have proven statistically that the entangled spin is created during the measurement. This measurement either kills the pro detection spin, either coalesces with the pro-detected spin if we measure the particle at a very abstuct-low enegy level [also then we have reading spin noise]

so yes, the spin is produced during measurement, but that does not mean that a particle has no spin. Mathematically even the non collapsed wavefunction requires a spin, because that angular momentum is an oscillation of nothingness itself, so we have something called field of one particles energy level.

So if we knew all spins from big bang and after, and if we could calculate all Richard Feynman's diagrams, we could then predict all probable anwers, but that is against Heisenbergs uncertainty.

The Heisenbergs uncertainty does not kill spin before detection, it just make is uncertain to various beholders that have different personal time flow perception also called angular momentum also called spin/period duration for a particular beholder versus an external particle to interact. — Preceding unsigned comment added by (talk) 02:41, 30 June 2014 (UTC)

The talk page of an article is not the place to discuss your view of the validity of the concept that the article presents. —Quondum 05:11, 30 June 2014 (UTC)

One of the assumptions made by the relative state formulation?[edit]

The article says "The first is that the wavefunction is not simply a description of the object's state, but that it actually is entirely equivalent to the object, a claim it has in common with some other interpretations." Is that actually stated in Everett's writing or did that come later? What's the significance of that assumption in the article? MazeHatter (talk) 13:27, 30 July 2014 (UTC)