Quantum Theory and The Many Worlds Theory

[YesNo]

Not a single one of these objections has the slightest force against the Many Worlds interpretation, and indeed every one of them betrays a total misunderstanding of it. Many Worlds is fully local and deterministic (unlike Copenahagen), and does not contradict the conservation laws. Nor does it contradict Occam's Razor at all. Not that the razor is any kind of law or anything to be paid much attention to in the first place.

I have been looking at Michael Clive Price's "The Everett FAQ" as one of footnotes in the Many Worlds Wikipedia article: http://www.hedweb.com/manworld.htm#ockham%27s

It is not convincing, but then perhaps I need more details.

I don't see the non-locality nor the indeterminate nature of the Copenhagen interpretation as problems. I do see the parallel universes however as problematic because I see no evidence for their existence except as a way to add determinism to QM.

In the Everett FAQ, Price writes under Q21:

The multiplicity of worlds predicted by the theory is not a weakness of many-worlds, any more than the multiplicity of stars are for astronomers, since the non-interacting worlds emerge from a simpler theory.

The main problem is that we can see stars but we cannot see these other worlds, unless we are watching Red Dwarf.

I do see the benefit of MW as a way to highlight the issues around QM, sort of like the way the Schrodinger Cat paradox does, but I can't believe anyone takes this seriously. Perhaps I just don't know what MW is claiming.

[Cioran]

Al these interpretations (models) have their own supporters, not any of them are 'the truth', all of them 'work'. One model might be easier to use in one context, another in another, that's what working physicists do - use the model that works. They don't try and decide between them to see which is "best". Gribbin suggests the Copenhagen interpretation is not the right model to apply to the puzzle of Schrodinger's cat, but the many worlds interpretation works very well... So in trying to grasp the cat puzzle, I'd look at it through the lens of various interpretations and if one gets you to understanding it, then you can be happy! You then understand it! You don't have to understand it via all interpretations, because all interpretations work.

Many-worlds explains the cat so nicely, to a seven year old, that I recommend using that, and get over the "there's too many worlds!" complaint. I mean, there are too many galaxies, 100 billion when one seemed quite enough... so why not many worlds, why not multiverses... why not?

Scientists make models of reality that "work." If they don't work, the models are discarded.

QM works, that much is definite. Many scientists would dismiss the question of what it means -- what QM tells us about the ontology of the world, and of epistemology -- as unimportant. Others, principally philosophers, are not satisfied by this "shut up and calculate" approach. Indeed, Copenhagen is pre-eminently a "shut up and calculate" approach to QM

All the interpretations of QM are consistent with the observed facts. Therefore one is free to accept any interpretation, unless and until there can be empirical confirmation of one over the other. This might be possible, though currently it is not. MWI could be confirmed or ruled out by use of a special computer (not currently within our technology) and a certain type of experiment. There may be other ways to gather empirical evidence for one or another interpretation.

Just to clarify:

Conservation objection: MWI is NOT a theory of branching or splitting worlds, no matter how many times this description has been used in the literature, even by those who ought to know better. New worlds are not "created" and hence there is no violation of the conservation laws. The universe is an isolated system, and the wave function encodes/describes the totality of it -- which happens to contain many worlds. None of these worlds are "brought into existence" by splitting. They simply are.


Spooky action at a distance: There is no spooky action at a distance in MWI. MWI in fact solves the problem of spooky action at a distance, showing it to be illusory. Spooky action at a distance depends on wave function collapse. There is no wave function collapse in MWI. There is just the wave function, which is the totality of reality.

Occham's Razor: The razor counsels that we not multiple assumptions unnecessarily in trying to explain some fact of reality. MWI is victorious under Occham, because it simplifies quantum theory, removing assumptions like hidden variables (which have been experimentally ruled out anyway). That fact that MWI multiplies worlds is irrelevant. Worlds are not assumptions. MWI is the victor if we invoke the razor.

Technical discussion at the following link (depending on your computer/browser, you may have to scroll side to side as well as up and down to read the whole PDF).

Many Worlds or Many Words?

It's worth noting also that Copenhagen, in addition to destroying determinism, locality and mind-independent realism, destroys cause and effect. This is easily shown. Two quantum-entangled particles are spacelike separated. Mary observes the state of one particle. Magically -- without any explanation whatsoever! -- her very act of observing the particle collapses the wave function, instantanelously across the entire universe if the two quantum entangled particles are that far apart -- and causes the result of the second particle that Sam later records.

But wait! Since the particles are spacelike separated, relativity theory shows that there is no objective fact of the matter about whether Mary looks at her particle first, collapsing the wave function and causing Sam to get his result, or whether Sam looks first and collapses the wave function and causes Mary to get her result! Two observers in different relative notion will disagree on whether Mary looked first or Sam looked first. Thus QM in conjunction with SR renders cause and effect meaningless.

MWI clears up this problem quite nicely. There is a world in which Mary looked first, and a different world in which Sam looked first. And no wave function is collapsed anyway. There are just different "pairings" of the particle states that are possible according to the wave function. The act of looking by either Mary or Sam causes nothing, under MWI.

[mal4mac]

I don't see the non-locality nor the indeterminate nature of the Copenhagen interpretation as problems. I do see the parallel universes however as problematic because I see no evidence for their existence except as a way to add determinism to QM.

I think it's all a matter of taste - you have a taste for Copenhagen, Cioran has a taste for MW. The fact is that both interpretations are correct! They are both models that work - one kid might prefer the lego robot, the other the meccano robot, but both work, even if one says "I can't stand bricks" and the other says "I can't be doing with screws."... but they both are good little robots...

[cacian]

This thread actually made me think of metaphysics.
the word "metaphysics" goes back to Aristotelean philosophy, Aristotle himself credited earlier philosophers with dealing with metaphysical questions. The first known philosopher, according to Aristotle, is Thales of Miletus, who taught that all things derive from a single first cause or Arche.
The science behinds it is to try and determine what is there and what it is like.

Arche meaning:

.Arche (ἀρχή) is a Greek word with primary senses 'beginning', 'origin' or 'first cause' and 'power', 'sovereignty', 'domination' as extended meanings.[1] This list is extended to 'ultimate underlying substance' and 'ultimate undemonstrable principle'.[2] In the language of the archaic period (8th-6th century BC) arche (or archai) designates the source, origin or root of things that exist. If a thing is to be well established or founded, its arche or starting point must be secure, and the most secure foundations are those provided by the gods-the indestructible, immutable and eternal ordering of things. In ancient Greek Philosophy, Aristotle foregrounded the meaning of arche as the element or principle of a thing, which although undemonstrable and intangible in itself, provides the conditions of the possibility of that thing.

[YesNo]

I think it's all a matter of taste - you have a taste for Copenhagen, Cioran has a taste for MW. The fact is that both interpretations are correct! They are both models that work - one kid might prefer the lego robot, the other the meccano robot, but both work, even if one says "I can't stand bricks" and the other says "I can't be doing with screws."... but they both are good little robots...

I think it might be possible to say that Heisenberg's matrix model and Schrodinger's wave model are equivalent and so it is a matter of convenience which one a physicist uses. I actually don't know if that is the case, but if they are equivalent the physicist would get the same results in all cases no matter which model they used.

However, these interpretations are different from a mathematical model and they conflict with each other. The Many Worlds and Copenhagen interpretations don't give the same results. One says there are many worlds. The other says there is only one. Since they are contradictory, they can't both be right.

I have just started reading cioran's reference to Max Tegmark's 1997 paper. Cioran brings up an interesting issue of cause and effect associated with non-local behavior that I hadn't thought about. Actually, this is the first time I've thought much about any of these issues.

It's worth noting also that Copenhagen, in addition to destroying determinism, locality and mind-independent realism, destroys cause and effect. This is easily shown. Two quantum-entangled particles are spacelike separated. Mary observes the state of one particle. Magically -- without any explanation whatsoever! -- her very act of observing the particle collapses the wave function, instantanelously across the entire universe if the two quantum entangled particles are that far apart -- and causes the result of the second particle that Sam later records.

But wait! Since the particles are spacelike separated, relativity theory shows that there is no objective fact of the matter about whether Mary looks at her particle first, collapsing the wave function and causing Sam to get his result, or whether Sam looks first and collapses the wave function and causes Mary to get her result! Two observers in different relative notion will disagree on whether Mary looked first or Sam looked first. Thus QM in conjunction with SR renders cause and effect meaningless.

MWI clears up this problem quite nicely. There is a world in which Mary looked first, and a different world in which Sam looked first. And no wave function is collapsed anyway. There are just different "pairings" of the particle states that are possible according to the wave function. The act of looking by either Mary or Sam causes nothing, under MWI.

Are there worlds in MWI where the assumptions of non-locality are false?

I could see this happening, for example, if Mary's entangled particle no longer has a pair in her world. Sam and his observation would be in some other world. Or it could occur if Mary looks first, gets a result, but Sam gets a result that is not consistent with non-locality. The reason I think this should be possible is because of the cause and effect criticism you made. It also appears the MWI does not support non-locality except as an illusion. I would expect in some world the illusion would not exist.

I found Max Tegmark's article interesting, but it mainly helped reinforce the vocabulary. I find it difficult to trust the article since Tegmark quoted a poll at the beginning of the paper that he admitted was unscientific and then used it as if it provided evidence of something.

[mal4mac]

However, these interpretations are different from a mathematical model and they conflict with each other. The Many Worlds and Copenhagen interpretations don't give the same results. One says there are many worlds. The other says there is only one. Since they are contradictory, they can't both be right.

They do give the same, right, results, otherwise the one that didn't would be rejected out of hand. Wave collapse or MW can't be detected experimentally, so about such things it's better to be silent, or just treat them as mental props that help you (perhaps) get (some) understanding of what is going on (though probably don't help much...)

Personally, I think a "no interpretation" approach might be most useful, and honest, for laymen, especially seven year olds. Just say what the actual experimental results are... in actual experiments like "double slit" and "Aspect". (Ignore that non-experiment with Schrodingers darn cat!) Then when particles go through the double slit one by one and give a wave pattern just fess up and say, "As Feynman says, even we physicists don't understand, can't even comprehend, why this happens, it goes against all our everyday understanding, and can never be comprehended like we can comprehend Newton's laws in a simple 3D force/reaction model, or any other model graspable by the human mind. But it happens, and our equations predict the results, and you can calculate them yourself if you study theoretical physics night and day from O level to MSc level..."

If you tell the seven year old "there is wave collapse" or "there are many worlds", this is lying. We don't know what happens!

[Cioran]

I find it difficult to trust the article since Tegmark quoted a poll at the beginning of the paper that he admitted was unscientific and then used it as if it provided evidence of something.

He did nothing of the kind. I've no idea where you got that idea.

[YesNo]

He did nothing of the kind. I've no idea where you got that idea.

This is what I'm referring to (http://arxiv.org/pdf/quant-ph/9709032v1.pdf)

At the quantum mechanics workshop to which these
proceedings are dedicated, held in August 1997 at
UMBC, the participants were polled as to their preferred
interpretation of quantum mechanics. The results are
shown in Table 1.
Interpretation Votes
Copenhagen 13
Many Worlds 8
Bohm 4
Consistent Histories 4
Modified dynamics (GRW/DRM) 1
None of the above/undecided 18
Although the poll was highly informal and unscientific
(several people voted more than once, many abstained,
etc), it nonetheless indicated a rather striking shift in
opinion compared to the old days when the Copenhagen
interpretation reigned supreme.

The part in bold is where Tegmark draws a conclusion from a poll that is unscientific. The part in red is what I find most troubling about this poll.

Later under the "III. C." section he writes:

One reason why experimentalists are becoming increasingly
positive to the MWI

On what basis, besides the unscientific poll he cites at the beginning of the paper, does he have to make this claim about experimentalists?

Is there any other article that you might recommend? I would like to know more about what this split actually is and how it relates to non-local entangled events. The statement Tegmark makes about what Everett did not claim is interesting:

At certain magic instances, the the world undergoes
some sort of metaphysical “split” into two branches
that subsequently never interact.

However, it is too vague to be useful.

[Cioran]

He did not tout the poll as providing evidence of MWI, merely to note that it was becoming a more mainstream idea among those who study the matter. That was 1997, and I expect it's even more mainstream now.

He's very clear in the paper: while (currently) there is no empirical way to distinguish between MWI and Copenhagen, or other various interpretations, which version you find more plausible might depend on whether you take a natural language or a mathematical view of reality. The mathematical view of reality favors MWI -- not to mention that Copenhagen is replete with unexplained magic, like consciousness magically without any observable mechanism collapsing the wave function instantaneously across the whole universe.

[mal4mac]

YesNo, why are you so troubled that some people are happy with many interpretations? It's well known in physics circles that people use whatever interpretation works best for the job at hand. Working physicists use MW today, Copenhagen tomorrow, whatever next week. I thought you were a fan of the 'model view of reality'? if so, what's wrong with people using different models - Lego today, Airfix tomorrow...

Everything in this area is vague, Tegmark is a really bright chap and usually the clearest on these matters... so if I were you I'd give up, you aren't going to find anyone to clear this mess up... I recommend reading Swift, Gulliver's travels, this is really Big Endian territory...

... Copenhagen is replete with unexplained magic, like consciousness magically without any observable mechanism collapsing the wave function instantaneously across the whole universe.

MWI is replete with unexplained magic, like universes magically splitting without any observable mechanism, and we can't even see these other universes.

Big Endian - Little Endian....

[Cioran]

MWI is replete with unexplained magic, like universes magically splitting without any observable mechanism, and we can't even see these other universes.

Big Endian - Little Endian....

As explained by Tegmark, the universes do not split. The wave function is the totality of reality, and it contains many diffrerent versions of the world.

[YesNo]

YesNo, why are you so troubled that some people are happy with many interpretations? It's well known in physics circles that people use whatever interpretation works best for the job at hand. Working physicists use MW today, Copenhagen tomorrow, whatever next week. I thought you were a fan of the 'model view of reality'? if so, what's wrong with people using different models - Lego today, Airfix tomorrow...

Everything in this area is vague, Tegmark is a really bright chap and usually the clearest on these matters... so if I were you I'd give up, you aren't going to find anyone to clear this mess up... I recommend reading Swift, Gulliver's travels, this is really Big Endian territory...

I'm just trying to understand. I don't really know what it means to be a fan of the model view of reality. Perhaps I was trying on an idea in the past. MWI still sounds too much like science fiction to me, but this is a literature forum.

He's very clear in the paper: while (currently) there is no empirical way to distinguish between MWI and Copenhagen, or other various interpretations, which version you find more plausible might depend on whether you take a natural language or a mathematical view of reality. The mathematical view of reality favors MWI -- not to mention that Copenhagen is replete with unexplained magic, like consciousness magically without any observable mechanism collapsing the wave function instantaneously across the whole universe.

Well, the Copenhagen interpretation is also a mathematical view of reality. The main difference between it and MWI is that MWI keeps all the outcomes, even those that don't happen, while CI just hangs onto what actually happens in the real world. Regardless of the existence of multiple worlds in which we supposedly exist, there is only one world that need concern us.

I think the MWI approach is interesting because it forces people to define their positions better. There is nothing like contention to clarify issues. And who knows? It may be right, but I have no intention of being the cat in a quantum suicide experiment.

[Cioran]

Here is a PBS interview from a few years ago about the Many Worlds that is very accessible to the lay reader (the Tegmark paper, not so much). It also talks about the shameful way Hugh Everett, who first mooted Many Worlds, was treated by some of the founders of original Copenhagen QM and their acolytes -- Einstein not among them, because he, alas, had died two years before Everett unveiled his theory which restored everything to 'QM that Einstein protested was lacking in it: determinism, realism, localism and no spooky action at a distance. Einstein opposed Copenhagen because, of course, Copenhagen is ridiculous. It's worse than magic or saying "God did it."' It is true that Copenhagen successfully "models" the world, in such a way that useful predictions can be made and we can build televisions (which depend on QM to work. So does your computer) This only goes to show that science is not (necessarily) about finding out the truth of the world, but only in making sucessful predictions that are instrumentally useful. Einstein, though, because he was a classical natural philosopher and not just a "shut up and calculate" modern scientist, wanted to find out how the world really was. He died two years before he would have gotten his answer from Everett.

ETA: of course, that is only in this branch he died before Everett unveiled MW. In others he lived and remarked upon it. But then again, Mitt Romney was elected last week somewhere on the wave function, and somewhere else Hitler won the war.

[mal4mac]

I'm just trying to understand. I don't really know what it means to be a fan of the model view of reality. Perhaps I was trying on an idea in the past. MWI still sounds too much like science fiction to me, but this is a literature forum.

I had the impression you believe there is no reality, there are only models. So neither Copenhagen or MW interpretation reflects reality, they are just models.

Quantum mechanics consists primarily of mathematical equations describing the world of the very small. This is something that it does very well, with only one problem; these equations defy common sense. Hence the scramble to provide interpretations like "many worlds" theory or the Copenhagen Interpretation. From the point of view of instrumentalism such interpretations are unnecessary as all quantum theory needs to do is predict the behaviour of atoms and molecules.

So you can give an account of the results of the double slit experiment, and you can provide the equations that predict the results. But you can't provide an explanation that appeals to common sense. You say "I'm just trying to understand", but you never will, because nobody understands it, and you aren't the one person in seven billion who will make the conceptual leap to understanding (are you?)

"I think I can safely say that nobody understands quantum mechanics.", Richard Feynman, in The Character of Physical Law (1965) [... an exceptional book, by the way]

This is probably the most repeated quote in modern physics, often quoted wryly by aged physics professors to their over-avid students, followed by the second favourite quote "Shut up and calculate" - down to David Mermin.

So the main thing you need to understand, I suggest, if you and your seven year old are wanting to avoid being totally lost in frustrating perplexity, is that *you cannot understand it*. If he says "you mean *you* don't understand it dad," you can produce the key quote from the greatest physicist since Einstein...

P.S. If you tell your seven year old this, when he's a teenager, trying his hardest to prove dad & everyone wrong, he just might be that one in seven billion

Einstein, though, because he was a classical natural philosopher and not just a "shut up and calculate" modern scientist, wanted to find out how the world really was.

The Quixotic nature of that particular quest was revealed by Kant in his first critique. If you want something racier & more modern than that I recommend taking a crack at "Integral Spirituality" by Ken Wilbur. This also has its Quixotic aspects, but it takes Kant & post-modernism seriously.

[YesNo]

Here is a PBS interview from a few years ago about the Many Worlds that is very accessible to the lay reader (the Tegmark paper, not so much). It also talks about the shameful way Hugh Everett, who first mooted Many Worlds, was treated by some of the founders of original Copenhagen QM and their acolytes -- Einstein not among them, because he, alas, had died two years before Everett unveiled his theory which restored everything to 'QM that Einstein protested was lacking in it: determinism, realism, localism and no spooky action at a distance. Einstein opposed Copenhagen because, of course, Copenhagen is ridiculous. It's worse than magic or saying "God did it."' It is true that Copenhagen successfully "models" the world, in such a way that useful predictions can be made and we can build televisions (which depend on QM to work. So does your computer) This only goes to show that science is not (necessarily) about finding out the truth of the world, but only in making sucessful predictions that are instrumentally useful. Einstein, though, because he was a classical natural philosopher and not just a "shut up and calculate" modern scientist, wanted to find out how the world really was. He died two years before he would have gotten his answer from Everett.

ETA: of course, that is only in this branch he died before Everett unveiled MW. In others he lived and remarked upon it. But then again, Mitt Romney was elected last week somewhere on the wave function, and somewhere else Hitler won the war.

When I encounter science fiction containing ideas of parallel universes, I previously thought this was some nonsense these authors came up with. I didn't realize anyone actually believed other worlds were true. Also, when I heard the Schrodinger's Cat paradox, I didn't think that anyone believed this actually happens to a real cat. Apparently, the MWI supporters believe that a real cat in the experiment actually is still alive in some other world.

As far as "spooky" stuff goes, what MWI does is replace spooky action at a distance with spooky other worlds, which is actually spookier in my opinion.

mal4mac suggests I might be an "instrumentalist" which is what I suspect I am. Since all of these interpretations work, it is more like a religious choice which interpretation one prefers. Hmmm, Krishna or Jesus?

-------

Just thought of something! Perhaps Occam's Razor should be modified or why not create a new razor, call it the YesNo Razor , that says the theory with the least spooky stuff is better all other things being equal.