Talk:Many-worlds interpretation/Archive 3

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I'm a little unhappy with use of the word local to describe Schrodinger's equation. Locality could mean

  1. "finite propagation speed".
this was what I meant. And of course the finite limiting speed is the speed of light. What this translates to is that the physical equations are covariant in the relativistic sense (Lorentz invariant or generally covariant). --Michael C Price 16:28, 25 May 2006 (UTC)

However, solutions to Schrodinger's eqn do not posses finite propation speed.

True, but then the Schrodinger equation is not relativistic and is superseded, at higher energies, by the Dirac equation or the Klein-Gordon equation, depending on the spin of the particle -- these equations are Lorentz invariant. Quantum field theories are also always lorentz invariant. And beyond this super-gravity, loop-gravity, strings etc etc is/are widely expected to exhibit general covariance, at the very least, when finalised.
It is perfectly possible to write a nonrelativistic quantum field theory. Just second-quantize a nonrelativistic single particle theory. In fact, solid state physicists use such models.
You're quite right, non-relativistic QFTs exist; I was thinking of fundamental physics (my background, sorry). My mistake. --Michael C Price 17:11, 25 May 2006 (UTC)
Your argument that "it's only an approximation" doesn't seem to mean much. All of physics is only an approximation, and the notion that all theories must be exactly Lorentz invariant is one which must be experimentally tested. Lorentz invariance may itself be only an approximation which breaks down at the Planck scale.
Very likely, yes, and we shall have see whether MWI applies to the TOE when it is complete. We can only wait.... But in the meantime we can categorically state that it is applicable to all our versions of QFT. --Michael C Price 17:20, 25 May 2006 (UTC)
Double special relativity is not a ToE, it's simply a postulate. It may have some justification from loop quantum gravity, which is also not a ToE. If you want to claim that MWI only works for Lorentz invariant theories, you're admitting a fundamental flaw. I don't think you believe that though, and I don't think the article should go that way. However, your explanation below that some attention must be paid to the relativistic case sounds reasonable to me. So the position is this: MWI can be applied to relativistic quantum mechanics just as well as it can be to nonrelativistic quantum mechanics. This is not a function of the fact that non-relativistic quantum mechanics is an approximation to relativistic quantum mechanics, but rather just follows from the fact that how you interpret measurement is not affected by the symmetry group of your theory. Is that accurate? -lethe talk + 17:47, 25 May 2006 (UTC)
Accurate and eloquent. Cut and paste into the article? --Michael C Price 17:55, 25 May 2006 (UTC)

I would suggest that we don't limit ourselves to relativistic theories in this article, and there's no reason not to prefer discussion based on the (non-relativistic) Schrödinger equation.

There is such a reason, because unless we mention the relativistic angle critics will always complain that MWI can't be relativised. I know it is an irrelevant issue, but it keeps being raised. Locality is too important to ignore. Collapse being superluminal is an issue that has to be addressed. --Michael C Price 17:20, 25 May 2006 (UTC)

So let's just stop using the word "local" in this sense. -lethe talk + 16:54, 25 May 2006 (UTC)

This is one of the reasons why I've tried to reduce the article's dependence on the Schrodinger equation.
clearly the statement about locality was more ambiguous than I had realised. Is the solution to alter the principle of locality page? --Michael C Price 16:28, 25 May 2006 (UTC)
Yes, I think that's a good idea.--CSTAR 16:32, 25 May 2006 (UTC)
  1. "micro-locality" which means that singularities of solutions (as described by the so-called wave-front set -- this is a subset of phase space as opposed to configuration space. It was defined by Hormander, Duistermaat, Maslov, Guillemin et-al) propagate at finite speed. It is known by the theory of Fourier integral operators that the Schrodinger eqn is micro-local in this sense.
  2. Or it could just mean that the equation is given by local operators, that is differential operators.
  3. If locality refers to something about the EPR paradox, then I think that may be a little misleading,

--CSTAR 15:38, 25 May 2006 (UTC)

PS I realize it has been suggested I am "obscure" and I apologize if something above is "obscure". However, I can't find a better way of saying it briefly. It's an advantage in WP that many people with different backgrounds get to work together in writing an explanatory piece of text (the article) and I think we should try to use it to the fullest to produce a readable and highly accurate document.--15:48, 25 May 2006 (UTC)
CSTAR, could you say which phrase in the article you're complaining about? Is it "local continuous time evolution a system that obeys Schrödinger's equation"? The word local in that sentence is a link to local realism, so this complaint is not resolved by saying that the Schrödinger equation is only an approximation of a relativistic equation (which is a cop-out anyway). -lethe talk + 16:50, 25 May 2006 (UTC)
I meant it in these passages
  1. The probabilistic, non-unitary, non-local, discontinuous change brought about by observation and measurement.
  2. The deterministic, unitary, continuous time evolution of an isolated system that obeys Schrödinger's equation (or nowadays some relativistic, local equivalent).
However, I'm satisfied with Michael C Price's response (or maybe "cop-out) because that response is really the best one can hope here. I just wanted to register my misgivings and get some feedback from other contributors.
Here's why I'm bothered: The dynamics of an open quantum mechanical system is given by the Lindblad equation which is a (trace-class) operator valued evolution equation. This eqn gives the time evolution of a density state of an open system just as Schrödinger's eqn gives the time evolution of a closed system. In fact, this eqn is what I would suggest is the purely mathematical rendition of CI. It's not clear to me that Lindblad is any less local than Schrödinger. To show my ignorance here, I'm not sure what the relativistic analog of Lindblad is (although one could play some formal mathematical games I come up with something that looks like it). Anyway these are just some thoughts, or perhaps (as somebody famous once said,) "throwing some random mathematical names around".--CSTAR 03:38, 26 May 2006 (UTC)
I'm not sure either about the locality of Lindblad or of its relativistic equivalent, although my guess is the first is not local and the second, if it exists, is. This raises the question (which lethe raised) of fundamental vs solid-state physics and dissipative open vs closed systems. The article needs a statement, somewhere, about this. Perhaps a caveats section? --Michael C Price 06:23, 26 May 2006 (UTC)

Altered the use of local to exclude Schrodinger eqn --Michael C Price 17:11, 25 May 2006 (UTC)
Thanks. I agree that it's better.--CSTAR 03:38, 26 May 2006 (UTC)

Accessability & Ease of Understanding

I don't find this article at all accessable. It strikes me more as an entry for an advanced science textbook than one for an encyclopedia.

--shockeroo 00:04, 05 Jun 2006 (GMT)

I agree. We're trying to make it more accessible without losing the more technical stuff; it's better than it used to be. Have patience. --Michael C Price 07:27, 5 June 2006 (UTC)

Uncited no boundary claim

The advantages of MWI section says: While MWI does not quite generate the kinds of worlds necessary to justify the anthropic principle, it is a step on the way to Stephen Hawking's No Boundary Proposal and Max Tegmark's All Universe Hypothesis which do justify the anthropic principle[citation needed].

The No Boundary Proposal is just a conjecture about the initial conditions; I don't see the connection with MW, except insofar as it stems from quantum cosmology. Perhaps the latter should be stated as a benefit of MW instead. If no citation appears shortly I'll change the text to reflect this.--Michael C Price 07:27, 5 June 2006 (UTC)

Done. --Michael C Price 10:23, 5 June 2006 (UTC)

observation has no role?

"The relative-state interpretation makes two assumptions. 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. The second is that observation or measurement has no special role, unlike in the Copenhagen interpretation which considers the wavefunction collapse as a special kind of event which occurs as a result of observation."

This seems to be at odds with the statement "Each subsequent binary measurement (that is interaction with a system M) causes a similar split in the history tree. "

If a split is caused BY the measurement, then observation does in fact still play a special role. Multiplying outcomes, instead of collapsing them. I'd appreciate any comments on my stupidity in this matter.

Good observation. Observation plays no special role in the sense that the kind of state transformation needed to describe it is not different from the transformations that describe reversible time evolution.--CSTAR 15:43, 11 June 2006 (UTC)
Yes, any thermodynamically irreversible interaction with the environment causes a similar Everett-world splitting. The mechanism of the splitting is decoherence.--Michael C Price 11:02, 12 June 2006 (UTC)

Too many worlds

I hope you wont mind me saying that it seems fanciful, and unnecessary, to interpret each of the super-imposed states (or worlds) as if they are in some way on a par with the real world we experience. When I pluck a string on my guitar it vibrates in a complicated way that can be expressed mathematically as a sum of more simple vibrational modes through a Fourier expansion. This does not mean that the simpler modes are physically separate parallel states of the string- they just happen to provide a convenient mathematical representation.

Changing the subject slightly, guitars also provide an illuminating analogue to wavefunction collapse and measurements. If you strum a chord on a guitar and ask someone to whistle what they have heard you will find that, since it is impossible to whistle a chord, the whistler will whistle one of the notes of the chord. By varying the strength with which you pluck the individual strings in a chord you can cause the whistler to hear one particular note more prominently than another, and it is that note that they are most likely to whistle. So the effect is that the multiplicity of notes in the chord are then collapsed into a single note by the whistler in a way that parallels quantum measurements.

I'm sure a neurophysiologist could explain the auditory and vocal effects you mention via some mechanism(s), but what is the mechanism of wavefunction collapse? No-one ever's come up with an scientifically satisfying explanation of how wavefunctions collapse, although decoherence can explain why wavefunctions appear to collapse. This strongly implies that wavefunctions do not collapse. The remaining question is whether the wavefunction is real or just information; I reject the information POV since I don't see how updating our knowledge of the state of the world could cause single-particle interference-effects. Ergo I conclude the wavefunction is real and doesn't collapse. Hence all quantum outcomes are realised and we have many histories / many worlds / many universes -- call it what you will. --Michael C Price 19:24, 14 June 2006 (UTC)
It may seem "fanciful and unnecessary", but it's internally consistent. The alternatives to many-worlds all have serious problems. After half a century of trying to patch up the Copenhagen interpretation, many-worlds is looking better. It's one of those things in physics which seems wierd, but may not be wrong. Hawking has been quoted as saying "MWI is trivially true", which is not an endorsement but recognition of the internal consistency. --John Nagle 06:49, 16 June 2006 (UTC)

Hawking clearly accepts the truth of MW. His No Boundary Proposal is a clear extension of it. Hawking claims [perhaps erroneously] that in one universe Germany may have won WWII. Such a possibility may require different types of univereses than those predicted by MWs alone. When Hawking is asked does man have "free will," he answers all is determined, hence man cannot have free will. This can only be the case if Hawking believes the univese is ultimately entirely deterministic. And this can only be the case if MWs is true. Hawking points out if everything is determined there is no place for God. Again this indicates Hawking believes in a completely deterministic universe. MWs is not weird, it is natural. What is unnatural is for just one special universe to exist out of a near infinite number of more likely universes. What is unnatural is for the universe to be arbitrary, random, and limited. Is there just one star, one planet, one living thing? Or every possible star, planet and living thing? There is nothing fanciful or unnecessary about MWs.

There first time I heard there might be life on other planets, I thought that was fanciful and unnecessary. Then I realized, that is much more likely than our planet being the only planet in the universe capable of sustaing life. Our star is not unique, our galaxy is not unique, it is very unlikely our planet is unique, and very unlikely our universe is unique. Why should there just be one universe when so many are possible?

Michael D. Wolok 09:40, 18 June 2006 (UTC)

Michael, many of the matters you raise are not as straightforward as you present; consequently it is inevitable that they will be reverted if inserted (lost along with everything else in the same edit, since that is the easiest course of action for the reverter). For instance you say:
When Hawking is asked does man have "free will," he answers all is determined, hence man cannot have free will. This can only be the case if Hawking believes the univese is ultimately entirely deterministic. And this can only be the case if MWs is true.
But the existence of free-will has, IMO and that of many others, nothing to do with determinism but rather more to do with how we define free will. Also there are interpretations of QM that claim determinism (e.g. Bohm, Cramer and others). Statement to the effect that "determinism implies MWI" will be immediately reverted by their proponents. I know it is tiresome, and seems like a waste if time, to take into account everyone's else POV and consider what will be NPOV, but is predominately your own time you are wasting when your edits are lost. --Michael C Price 10:14, 18 June 2006 (UTC)

Didn't Lethe deny the existence of "classical physics":

"Classical physics is physics based on principles developed before the rise of quantum theory, usually including the special theory of relativity and general theory of relativity." --Wikipedia

When I referred to "classical physics" before, Lethe said there was no such thing, he said the term "classical physics" had no meaning. tsk, tsk, tsk.

Michael D. Wolok 09:18, 18 June 2006 (UTC)

I don't recall Lethe saying that. But what's the relevance; shouldn't you take that up on his or your talk page? --Michael C Price 09:38, 18 June 2006 (UTC)

BTW Michael, I've left some advice for you, a few hours ago, on your talk page. I hope you find it helpful. Regards, --Michael C Price 09:46, 18 June 2006 (UTC)
I have never claimed that classical physics does not exist, nor do I know what a claim like that would even mean. -lethe talk + 09:48, 18 June 2006 (UTC)

Here it is!

I wrote:

> 2. "[MWI] Returns quantum mechanics to a classical theory"

Lethe wrote:

> 2. "[MWI] Returns quantum mechanics to a classical theory" is patently false -lethe talk +

Michael Clive wrote:

> It depends on the definition of "classical".

Lethe wrote:

> Well, can you propose a definition of "classical" which allows MWI to be considered a classical theory? I know of no such definition.

Well, Lethe, look at the definition given by Wikipedia to "classical physics." According to MWI, quantum mechanics becomes just another theory in classical physics.

Lethe wrote:

> The most concise definition of "classical" that I could give would "algebra of

> observables is commutative". Quantum mechanics does not satisfy this definition,

> and using the MWI interpretation does not save it. -lethe talk +

"Classical physics" or a "classical theory" refers to theories that are determinstic.

Michael D. Wolok 09:57, 18 June 2006 (UTC)

No, that's not what "classical" means. Consider, for example, classical statistical mechanics. As I said, "classical" means that the algebra of observables is commutative. -lethe talk + 10:08, 18 June 2006 (UTC)
I believe the advantages section is balanced and fair on the subject:
MWI allows quantum mechanics to becomes a realist, deterministic, local theory making it more akin to classical physics (including the theory of relativity).
--Michael C Price 10:32, 18 June 2006 (UTC)

Intro and first 2 sections reworked?

I am a bit concerned about the state of the article, so I've rewritten the early sections. If no one objects then I'll paste it over the article (and delete from here). Here it is:

It generally looks fine by me. I may have some quibbles here and there. --CSTAR 14:12, 19 June 2006 (UTC)
Done! --Michael C. Price talk 15:20, 19 June 2006 (UTC)

comments to Price's new version

I think Price's intro section (first paragraph) is a marked improvement on what is currently in the article, and I move that it be adopted. Some copyediting and wording revisions suggested themselves to me, should I edit the version as it sits on the talk page, or wait for it to go into the article? Anyway, about the rest, could you maybe highlight some of the changes? I am having a hard time picking out what changes have been made to the last section for example. Though of course this means that the revision must be conservative about keeping the work of others which is presently in the article, so I support that. -lethe talk + 14:33, 19 June 2006 (UTC)

Thanks for both votes, OK I'll copy it into the article when I've finished this message, that way any minor changes (get ready CSTAR, Lethe!) can go in straight. It should also enable folks to do a diff on it. You right, though, I didn't change last section that much, although I felt it does duplicate the wavefunction collapse article a bit. Not sure what to do about that, though. --Michael C. Price talk 15:11, 19 June 2006 (UTC)
At the last second I decided to short the title of section 2. Every thing as it was here (about to be deleted). --Michael C. Price talk 15:19, 19 June 2006 (UTC)

It is not the nature of nature to do things just once.

It is not the custom of nature to do things just once. From what we are able to observe, nature is fond of repeating the same thing over and over again with minor and major variation. Near infinite variation of a theme is nature's way. It is much more likely our universe is just one snowflake among countless others that have fallen and will fall, than the only snowflake to ever exist. If science has taught us anything, it has taught us that we are not special. Our planet is not the only planet. It is not at the center of the universe. Our star is not the only star. And it is not at the center of the universe. Our galaxy is not the only galaxy. And our galaxy is not at the center of the universe. It would indeed be remarkable if our universe was the only universe, and the centerpiece of all creation.

True, a persuasive argument, but outside the scope of quantum theory and therefore MWI. However well within the scope of the multiverse -- you could mention it there. --Michael C. Price talk 17:42, 19 June 2006 (UTC)

Gee Whiz, I had no intention of mentioning it anywhere but here on this discussion page. I was addressing John Nagel's comment that Many Worlds is strange!

Michael D. Wolok 03:12, 20 June 2006 (UTC)

They say if enough monkeys typed randomly for a long enough period of time, they would produce Wikipedia--if in fact, this is not all readdy the case. It seems very likely our fine-tuned universe exists because given infinite time, nature has had the means and opportunity to produce countless universes big and small. Given the law of large numbers, even the improbable becomes likely. If ink is spilled an infinite number of times, it will eventually produce a coherent page. It is very likely our universe is just such a page.

Michael D. Wolok 17:34, 19 June 2006 (UTC)

Dear Michael Price

Dear Michael Price,

I don't see we have any disagreement. I don't know why you keep trying to make it appear as if we do.

We disagree about some of the "facts", such the relevance of the no-boundary theorem, the implications of determinism etc. We also disagree about Wikipedia's policy. I think they are good policies: NPOV, NOR etc . You seem to disagree. We also disagree about what amounts to an effective writing style. Now I could go on and on -- but I feel that would dilute the message!! --Michael C. Price talk 23:02, 19 June 2006 (UTC)

You wrote: > Statement to the effect that "determinism implies > MWI" will be immediately reverted

I never edited the article in such a way, nor did I ever ask the article be edited in such a way.

Stephen Hawking believes in many histories. His belief that man has no free will stems from his belief all histories exist. I agree with you that the existence of "free will" depends upon how you define the term. But it is clear from

      • Hawking's*** answer to the question of the

existence of free will, that Hawking believes in countless universes with different histories. Now, maybe this is not exactly an endorsement of Hugh Everett's Many Worlds, but it's close. In light of other comments made by Hawking, it seems he thinks Hugh Everett's Many Worlds is the straightforward interpretation of QM.

I would place everything you have written in your FAQ in this article. I would be happy to do so.

I am not happy with the current section "Advantages of Many Worlds" for a variety of reasons, but would like to get others involved before going further.

I would like to see the section read as follows:

Advantages of MWI

If Hugh Everett's theory was just another interpretation of Quantum Mechanics it would have no followers, especially since it proposes the existence of countless other universes which theoretically can never be observed. Because it is not falsifiable it seemingly violates Popper's criteria for a good scientific theory. The reason it has so many adherents is because it offers numerous advantages over the Copenhagen Interpretation, among which are the following:

1. Quantum mechanics becomes a deterministic theory making it more compatible with the theory of relativity and all other physics theory to date which are all deterministic. The Copenhagen Interpretation introduced indeterminacy and randomness into science. Aside from the Copenhagen Interpretation of Quantum Mechanics there is no scientific theory that includes indeterminacy or randomness. Einstein particularly objected to this aspect of the Copenhagen Interpretation. In response to it, he said, "God does not play dice with the universe."

2. It eliminates the "measurement problem."

3. It eliminates Von Neumann's "boundary problem": where to draw the line between the micro world where quantum mechanics applies, and the macro world where it does not. Shortly before his death in 1953, Albert Einstein wrote: "Like the moon has a definite position whether or not we look at the moon, the same must also hold for the atomic objects, as there is no sharp distinction possible between these and macroscopic objects."

4. It eliminates the special place for an observer and human consciousness.

5. It restores objective reality of the universe between measurements. Shortly before his death, Albert Einstein also wrote: "Observation cannot CREATE an element of reality like a position, there must be something contained in the complete description of physical reality which corresponds to the possibility of observing a position, already before the observation has been actually made."

6. The wave-particle duality paradox evaporates. It does away with Bohr's "principle of complementarity." It simply and naturally explains the double-slit experiment. Richard Feynman said, "[the double-slit experiment] has in it the heart of quantum mechanics. In reality it contains the only mystery." David Deutcsh wrote: ". . . the argument for the many worlds was won with the double-slit experiment."

7. Schrodinger's Cat paradox evaporates.

Einstein's main objections with quantum mechanics had more to do with the Copenhagen Interpretation, than with quantum mechanics itself. Einstein mainly objected to quantum mechanics because it was not a deterministic theory, and it required doing away with classical realism. Hugh Everett's theory automatically eliminates both these objections. While MWI does not quite generate the kinds of worlds necessary to justify the anthropic principle, it is a step on the way to Stephen Hawking's No Boundary Proposal and to Max Tegmark's All Universe Hypothesis which do justify the anthropic principle. The anthropic principle resolves the fine-tuning problem, and how our universe started with such low entropy.

John Wheeler, a famous physicist and Everett's thesis advisor, put his name on Everett's thesis, but later criticized it as "carrying too much metaphysical baggage." Hugh Everett left physics because of the poor reception his theory received. It initially attracted no followers and was largely ignored. It gained adherents in the 1980s, and today is considered a mainstream interpretation of Quantum Mechanics. Its popularity continues to grow.

Apparently not. Check out, and the err.. associated survey The Ensemble Interpretation seems on the way to being the most favoured, with the MWI last. Kevin aylward 11:43, 27 October 2006 (UTC)

I think my wording could be improved, but I think the additions I want to make, make the article clearer especially for the layman. As it is written now, it is geared at the level of the advanced graduate student, not the average Wikipedia reader.

By lumping different points together you weaken the argument for Many Worlds. If someone disagrees with one part of a point, the whole point is lost. Therefore, it is better to list different advantages under their own point. There are many reasons proponents favor Many Worlds. Just because someone disagrees with one reason to favor the theory, doesn't mean they won't favor the theory for the other reasons. Any reason to favor the theory is a reason to favor the theory.

The quotes I listed are relevant. There are no ifs ands or buts, if Many Worlds is true, the paradox of wave-particle duality disappears.

This is already stated in the Advantages section. --Michael C. Price talk 22:57, 19 June 2006 (UTC)

The strained, unnatural principle of complimentarity is unneeded. The "principle of complimenarity" may not be an outright contradiction, but it is certainly strained and ad hoc.

Depends what you mean by complementarity. Having debated with Afshar I'm coming to the conclusion that complementarity means no more than the Heisenberg uncertainty relations -- but they still appear in MWI. --Michael C. Price talk 22:57, 19 June 2006 (UTC)

Warmest and kindest regards, Michael

Michael D. Wolok 18:16, 19 June 2006 (UTC)

That's an excellent summation. Let's use it. --John Nagle 18:22, 19 June 2006 (UTC)
I disagree with Nagle. Let's please stick with the text in the article. For one thing, the claim that all physics is deterministic is incorrect. Copenhagen quantum mechanics is perfectly compatible with relativity, so the claim of MWI being more compatible may be objectionable. I don't know what the right wording is to describe MWI's privileged relationship with SR, but this isn't it. And numbers 2, 3, and 4 say exactly the same thing. The list is needlessly repetitive. -lethe talk + 18:43, 19 June 2006 (UTC)

Thank you John. I am the one responsible for adding the section Advantages of MW. "Lethe" immediately reverted the whole thing, saying everything I wrote was patnently false, and poorly written. I wrote Professor Max Tegmark who agreed with me on just about everything I wanted to addd. I posted Max Tegmark's email to the discussion page here, then added back my addition with Professor Tegmark's corrections. Others modified and improved it. Lethe then reverted it all, again without explanation. Ever since, I have been trying to get an advocate and mediation. I called Jim Wales. I wrote the Wikipedia foundation. I have been trying to get other editors involved to no avail, though I may be gaining some traction now. By the way, Professor Tegmark is a renown Ph.D. cosmologist and Professor at MIT who has written several articles for Scientific American and has many published peer reviewed articles.

Warmest and kindest regards, Michael D. Wolok

Lethe has been openly hostile to me and every word I have tried to add to Wikipedia.

Michael D. Wolok 18:54, 19 June 2006 (UTC)

I think you are unfairly targetting lethe here. I think the position he is sustaining is the consensus view of contributors that have worked on this article.--CSTAR 19:12, 19 June 2006 (UTC)
I agree with CSTAR and Lethe; the suggested changes are needlessly repetitive, make lots of unveriable assertions, is not NPOV and has a general amateurish appearance. Please don't take this as a personal attack; it's simply my evaluation of what is written. It's a case of where more is less. Sorry. Having said that there may be something in there which isn't in the Advantages section; I'll read through and see what I can extract. --Michael C. Price talk 22:09, 19 June 2006 (UTC)

Hi Michael,

Can you point out to me which of my changes are needlessly repetitive?

It's already been pointed out that:
And numbers 2, 3, and 4 say exactly the same thing.

Can you list the unverifiable assertions I made, and give me a chance to support them?

The very first clause is unverifiable (and I believe false):
If Hugh Everett's theory was just another interpretation of Quantum Mechanics it would have no followers
since almost any interpretation will have some followers. Do you accept that this is unverifiable? If you do then apply the same reasoning to the rest of your comments. If you don't then we have to debate it further. Which is it?

Can you point out what you believe is not NPOV?

The same clause is also not NPOV for pretty much the same reasons.

You say it has a general amateurish appearance. John Nagel thought it was excellent. Perhaps, the truth lay somewhere in between. If you think the appearance is amateurish perhaps you can make it sound more professional. "Amateurish appearance" is not a fatal flaw.

See my later comments on effective writing.

I think my addition contains a lot of information that is not in the article,

I disagree. I compared your text with what was there and I don't see anything new. Remember there is a lot of implicit information that reader can access by linking through. A lot of my time has been spent updating the linked articles, such as:
EPR paradox
quantum decoherence
quantum measurement (now linked directly from "Advantages")
Schrödinger's cat
wavefunction collapse (just added!)
wave-particle duality
and nested linked articles such as:
Bell's theorem
Bohmian mechanics
correspondence principle
counterfactual definiteness
interpretation of quantum mechanics
introduction to quantum mechanics
quantum mechanics
Universal wavefunction
and many more so as to avoid cluttering up the MWI article. Which also improves Wikipedia generally -- as is intended -- which is why it is a Wiki policy, I believe.

and should be in the article for readers to understand the significance of the theory. Let's discusss this. I am willing to abide by your opinion. You are the expert on Hugh Everett's theory, not I. Can you reason with me? I am not a hard person to reason with.

Then start listening to the advice that people are giving you and STOP accusing them of attacking you. You are not giving the appearance of being reasonable and you have only yourself to blame if people lack the patience to deal with you; in fact I'm amazed at how reasonable people have been towards you. --Michael C. Price talk 06:07, 20 June 2006 (UTC)

Reading your Hugh Everett FAQ was the happiest day of my life.

Thanks, that means lot to me. I believe part of the reaon why you (and others) like the FAQ is because it is clearly written and non-repetitive; one way it avoids repetition is by linking to other answers. I once went on a business course called "effective writing" which was all about how to, well, write effectively. The main points were the ones that I've already told you: don't repeat yourself (except in summaries and conclusions); less is more -- avoid verbosity, especially long discombobulating adjectives; provide only a few strong reasons rather than a mixture of strong and weak reasons. There was more but I won't go on!! The amazing thing is that "effective writing", once internalised, leads to "effective thinking"; the course changed my life (I'm not joking). I believe we can all benefit from effective thinking. Try it and see.

Let's look at my addition sentence by sentence. Tell me what you don't like, and why you don't like it. Perhaps, I will learn something. I think you will find me quite reasonable.

Let's hope so. We all have much to learn. I have only critiqued the first few clauses since I believe the same lessons can be applied through out. If we can agree on those then we can move forward. --Michael C. Price talk 06:07, 20 June 2006 (UTC)
Note: I've just updated the Advantages section. --Michael C. Price talk 07:04, 20 June 2006 (UTC)

Warmest and kindest regards, Michael

Michael D. Wolok 02:57, 20 June 2006 (UTC)

I should add, though, that I agree with Michael Wolok that sections of the article are unreadable to the lay reader and (I suspect) to the more technical readers as well. --Michael C. Price talk 22:48, 19 June 2006 (UTC)

I changed the MWI Advantages to indicate that it is only an allegation that MWI eliminates non-locality. There are peer reviewed, credible arguments that QM violates locality inherently. These arguments claim to dispense with CFD, and the other usually assumptions. Yes, some have claimed that these new proofs have holes in them, yet still, these refutations have been refuted. So, it is simply not settled by the professional experts whether or not QM violates locality. Kevin aylward 11:37, 27 October 2006 (UTC)

Lethe violates all these Wikipedia rules

To assume good faith is a fundamental principle on Wikipedia. As we allow anyone to edit, it follows that we assume that most people who work on the project are trying to help it, not hurt it. If this weren't true, a project like Wikipedia would be doomed from the beginning.

So, when you can reasonably assume that something is a well-intentioned error, correct it without just reverting it or labeling it as vandalism.

Especially, remember to be patient with newcomers, who will be unfamiliar with Wikipedia's culture and rules. Correcting a newly added sentence that you know to be wrong is also much better than simply deleting it. You should not act like their mistake was deliberate. Correct, but don't scold.

Avoidance The best way to resolve a dispute is to avoid it in the first place.

Be respectful to others and their points of view. This means primarily: Do not simply revert changes in a dispute. When someone makes an edit you consider biased or inaccurate, improve the edit, rather than reverting it. Provide a good edit summary when making significant changes that other users might object to.

You might like to learn about another policy we have. It's called assume good faith, and one might argue that you are violating it now. Nevertheless, I'm happy to see that you're raising your complaints here on the talk page where the dispute is, instead of spreading it across hundreds of users' talk pages. -lethe talk + 19:30, 19 June 2006 (UTC)

Actually, Lethe, I always assume good faith. I didn't need Wikipedia to tell me that. But I am afriad you need to learn Wikipedia's policy assume good faith. That is what you have not done since the beginning. My first day editing, you blocked me for the 3RR, when all you had to do was identify yourself and explain the rule to me. You left a nasty note on my talk page. I didn't even know I had a talk page. You blocked me a second time for 3RR when I had not violated the rule. I did not revert the exact same material three times in one day. To this day, what I reverted remains reverted. Moreover, assume good faith means above all else not reverting other editors words in their entirety.

Michael D. Wolok 02:43, 20 June 2006 (UTC)

I disagree with your assessment of the situation. -lethe talk + 02:45, 20 June 2006 (UTC)

Naturally! Michael D. Wolok 14:02, 20 June 2006 (UTC)

Well let me be more explicit: you have grossly misinterpreted your own understanding of the MWI, my own position about MWI, the other editors' consensus about your additions. You have made wild and far-flung false accusations about me and others while continually asserting your own benevolence, you have disrupted Wikipedia process, and you have caused dismay to many friendly people around here. I for one can say I am near my wit's end. Please start assuming good faith, and please be more civil, and please calm down. -lethe talk + 14:13, 20 June 2006 (UTC)

If ten thousand monkeys . . .

If ten thousand monkeys, typed ten-thousand words per second for ten-thousand years, and produced Wikipedia, I wouldn't be a bit surprised.

That's a joke. Michael D. Wolok 20:56, 19 June 2006 (UTC)

If N monkeys, typed N words per second for N years, and produced Wikipedia, I wouldn't be a bit surprised.

As N → ∞ and the monkeys are independent and their keystrokes are independent uniformly distributed, that's a theorem. In fact you just need one monkey. --CSTAR 21:00, 19 June 2006 (UTC)

Lethe wrote: For one thing, the claim that all physics is deterministic is incorrect.

Lethe wrote: > For one thing, the claim that all physics is deterministic is incorrect.

I said all physics aside from the Copenhagen Interpretation of quantum mechanics is determinstic. If I am mistaken please correct me, and I will learn something. Roger Penrose and many other famous physicists seem to agree with me. I am struggling to understand why you say I am mistaken. You said I was patently in error before concerning statements I made that renown physicist Max Tegmark explicitly agreed with me on. I know you think you are infallible, but maybe, just maybe consider the possibility you could be wrong again.

Please, let's consider my addition and object to it on a sentence by sentence basis. If I am wrong, and you are right, I will have no problem modifying my addition or retracting it in its entirety if necessary. Let's discuss it.

Michael D. Wolok 03:07, 20 June 2006 (UTC)

I have said this before, but I will repeat myself for you: statistical mechanics is another nondeterministic theory. So not all physics outside of Copenhagen is deterministic. -lethe talk + 03:18, 20 June 2006 (UTC)

I have carefully read everything you have written, and did not notice this. Perhaps, I missed it. Is statistical mechanics nondeterministic? Or like chaos theory does it just imply non-computability. Just because a theory claims there are things that are non-computable does not mean the theory is nondeterministic and non-causal.

Michael Price, can you define for me again the definition of causality and determinism? I think I will go and see what Wikipedia has to say about these topics. It is my understanding that the CI of Quantum Mechanics introduced randomness into physics, that is one of the main reasons Einstein objected to QM. That is the reason for his famous quote: "God does not play dice with the universe." Something here does not add up.

Michael D. Wolok 03:29, 20 June 2006 (UTC)

Einstein knew very well about the nondeterminism of statistical mechanics. He wrote a seminal paper on Brownian motion in 1905. The reason Einstein objected to quantum mechanics but not statistical mechanics is that statistical mechanics was never put forth as a fundamental theory. It's easy to imagine that a deterministic fundamental theory might lead to a nondeterministic phenomenological theory through the law of large numbers, and that was the expectation until the advent of quantum mechanics. Quantum mechanics was then, and is still today, thought to be a fundamental description. Thus if quantum mechanics is nondeterministic, then God plays dice, while the nondeterminism of statistical mechanics does not have anything to do with God's gaming habits. This is an interesting topic to discuss, but does not belong in this article. The upshot remains this: there is physics outside of Copenhagen which is nondeterministic. -lethe talk + 03:40, 20 June 2006 (UTC)

UNTIL THE CI OF QM THERE WAS NO ****FUNDEMENTAL*** PHYSICS THEORY THAT WAS NOT DETERMINISTIC. THE MWI OF QM RESTORES DETERMINISM TO ALL FUNDAMENTAL THEORIES IN PHYSICS!!! Is this right???? I don't know why you are being so hard-headed and refusing to see what I am trying to say. You must realize that the MWI restores a kind of determinism to physics that the CI took away. All the randomness and indeterminism of QM comes from the collapse of the wave-function. If the wave-function does not collapse, it evolves in a completely determinstic way set forth by Schrodinger's equation. According to the MWI, the wave-function does not collapse, hence it is a completely deterministic theory, a theory Einstein may not have objected to on the grounds of "God playing dice with the universe." Why is this so hard to understand? UNTIL THE CI OF QM EVERY ****FUNDEMENTAL*** PHYSICS THEORY WAS DETERMINISTIC. THE CI CHANGED THAT. THE MWI OF QM RESTORES DETERMINISM TO ALL FUNDAMENTAL THEORIES IN PHYSICS!!! RIGHT??? GEESH!!! Why are you forcing me to pull teeth?

Michael D. Wolok 04:12, 20 June 2006 (UTC)

The reason we are having this debate is because you want the sentence "Quantum mechanics becomes a deterministic theory making it more compatible with [..] all other physics theory to date which are all deterministic". I see no way to make this sentence into something meaningful. It's not correct as it stands, because there are other nondeterministic theories. Would you prefer to compare quantum mechanics only to other fundamental theories? Because quantum mechanics is the only fundamental theory we have. I'm not focusing on semantics just to annoy you; the fact that other theories are nondeterministic seems to me a fatal flaw for this sentence, and the fact that these other theories are not fundamental (which doesn't really mean anything anyway) does not save it. -lethe talk + 04:39, 20 June 2006 (UTC)

It wasn't that particular sentence that I wanted, but the idea I was trying to express with that sentence, that is now in the article!!! This is what I was trying to say:

"MWI allows quantum mechanics to becomes a realist, deterministic, local theory making it more akin to classical physics (including the theory of relativity)."

Or put another way: "Quantum mechanics becomes a deterministic theory making it more compatible with [..] all other fundamental physics theories to date which are all deterministic."

I left out the word "fundamental," but that is what I meant. Up to CI of QM no physics theory implied that on a fundamental level the universe is not deterministic. The CI introduced a kind of randomness that did not exist before. MWI eliminates some of this randomness, making the universe more deterministic and more in accordance with every other fundamental theory in physics like relativity which is a deterministic theory. Relativity is a fundamental theory which is entirely deterministic. Newtonian physics has Laplacian determinism. Relativity has Laplacian determinism. According to the CI of QM, Laplacian determinism is violated. MWI does not quite restore Laplacian determinism, but it does restore some measure of determinism. There is less dice playing in the MWI of QM than there is in the CI of QM. Einstein probably would have had less objection to the MWI of QM than he had to the CI of QM. There are two famous Einstein quotes criticizing QM. One has to do with the fundamental randomness QM introduces, and the other has to do with lack of reality between measurements. The MWI does away with both these objections, making it seem like Einstein had more problem with the CI than he did with QM itself. We can only speculate what Einstein would have thought of the MWI. But from what we know, it seems to address his main objections to the theory.

Michael D. Wolok 09:17, 20 June 2006 (UTC)

This may have been an advantage historically; when we have to compare quantum mechanics' validity as a fundamental theory to those which preceded it (Newton's gravitation, Maxwell's electromagnetism). But this is of historical interest only. No one today believes that Newton's gravitation or Maxwell's electromagnetism is a fundamental theory, any more than they do classical statistical mechanics. So what exactly is it that you want to say? That this could have been counted as an advantage for MWI in 1915 if MWI had been invented then? Well that's just silly. Today, the only candidates we have for fundamental theories are quantum theories. Also, I'm not sure if the designation "fundamental" has any meaning on other than an esthetic level, so the whole point may be purely philosophical. -lethe talk + 11:27, 20 June 2006 (UTC)

Hawking defines "scientific determinism" as meaning: "something that will happen in the future can be predicted."

[I disagree with this definition. I think there is a difference between predictablity and causal determinism. Even in classical physics, the future of three bodies in a gravitational field can't be predicted. But there is still casuality and a kind of causal determinism. The CI removes causal determinism. The MWI in a certain respect puts some of it back, though not completely the way it was before QM. ]

Hawking states that even the uncertainty principle does not rule-out determinism "in principle", and says that quantum mechanics may very well allow the universe to be deterministic. He wrote:

"These quantum theories are deterministic in the sense that they give laws for the evolution of the wave with time. Thus if one knows the wave at one time, one can calculate it at any other time. The unpredictable, random element comes in only when we try to interpret the wave in terms of the positions and velocities of particles. But maybe this is our mistake: maybe there are no positions and velocities, but only waves. It is just that we try to fit the waves to our preconceived ideas of positions and velocities. The resulting mismatch is the cause of the apparent unpredictability." (conclusions section of A Brief History Of Time)

The funny thing about this is, this is something I believed long before I ever heard of Hawking or Everett. The first time I read this, the hair on the back of my neck stood up. Nobody is interested in my gut feelings, but I believe in most respects the universe is local and but in one special respect it is non-local. I believe entanglement exists because there is a hidden global symmetry. There is a balance that must be maintained.

It is my understanding that there is no such thing as a truly irreversible thermodynamic interaction.

Michael D. Wolok 03:35, 20 June 2006 (UTC)

Michael Price

Hugh Everett's Theory implies many universes. Hartle and Stephen Hawking's No Boundary Proposal implies many universes. Quantum Cosmology implies many universes. Feynman's sum-over-histories, path-integral approach implies light takes every route to get from here to there. Can you help me understand the connection here? I don't quite understand why Max Tegmark claimed Feynman's sum-over-histories did not support Hugh Everett's Many Worlds. I asked this question in sci.physics.research and got an answer that was hard to understand. I was referred to this Wikipedia article. LOL!

Michael D. Wolok 04:21, 20 June 2006 (UTC)

this you?. -lethe talk + 04:43, 20 June 2006 (UTC)
 :-) Ignore anything Charles Francis says; he's been in MWI-denial for decades! As for the answer to MW's question, Feynman's sum-over-histories is a mathematical formulation; it does not pass judgement on the reality of the wavefunction. MWI requires the wf to be real; that's what distinguishes MWI from consistent histories, for example. --Michael C. Price talk 09:48, 20 June 2006 (UTC)
Steve Carlip's response seemed reasonable to me. In short, the three issues are not related. -lethe talk + 11:13, 20 June 2006 (UTC)
Re User talk:MichaelCPrice's comment: MWI requires the wf to be real; that's what distinguishes MWI from consistent histories, for example.CSTAR 14:50, 20 June 2006 (UTC)

[misplaced old comment deleted]

I know we've discussed that before. I think we'll just have to agree to disagree on that one.
I've inserted the following into universal wavefunction
The thesis introduction reads:
Since the universal validity of the state function description is asserted, one can regard the state functions themselves as the fundamental entities, and one can even consider the state function of the entire universe. In this sense this theory can be called the theory of the "universal wavefunction," since all of physics is presumed to follow from this function alone.
The universal wavefunction is the wavefunction or quantum state of the totality of existence, regarded as the "basic physical entity"[1] or "the fundamental entity, obeying at all times a determinstic wave equation"[2].
  1. ^ Everett 1957, section 3, 2nd paragraph, 1st sentence
  2. ^ Everett [1956]1973, "Theory of the Universal Wavefunction", chapter 6 (e)
--Michael C. Price talk 18:21, 20 June 2006 (UTC)
For one I think the consistent histories formulation is more general mathematically.
Also note one of Adrian Kent's (supposed) PhD students' comments in the discussion section of consistent histories. Of course this doesn't prove anything, and as far as I can tell the comments are anonymous. --CSTAR 14:50, 20 June 2006 (UTC)

Lethe wrote: > Steve Carlip's response seemed reasonable to me. In short, the three issues are not related. -lethe

Now why did I think that would be the case? LOL!

Maybe, they are not not related. What could possibly have led me to think there might be any connection between them? Oh yeah, they all imply the existence of near infinite universes. I guess before the MWI, it was quite common for physics theories to predict a near infinite number of universes.

Michael, if Hugh Everett's theory is right does that automatically imply Feynman's sum-over-histories?

No, not at all. --Michael C. Price talk 15:38, 20 June 2006 (UTC)

Is Feynman's histories, the same histories as the "histories" in Hugh Everett's theory?

That depends on how you define them; they can be but it is best that they are distinguished. --Michael C. Price talk 15:38, 20 June 2006 (UTC)

Michael D. Wolok 13:55, 20 June 2006 (UTC)

Your sarcasm is unwarranted and unwelcome here. Please try to be more polite (WP:CIVIL). -lethe talk + 14:00, 20 June 2006 (UTC)

Ockham's razor

Regarding Price's recent edit: While I agree that MWI is more streamlined, and that this is an attractive feature, I'm a little queasy about citing Ockham's razor. Ockham's razor is the the reason quoted by opponents of MWI most often, in my experience, and it somehow feels like we're co-opting our critics' arguments, trying to pull the rug out from under them. Do we intend to have a "criticisms of MWI" section somewhere? Mention of Ockham in that section would satisfy me. Simply removing the citation to Ockham, but keeping the rest of the sentence might also satisfy me. I wonder what others think. -lethe talk + 11:17, 20 June 2006 (UTC)

I was thinking of adding a criticisms section, and you're right a different form of Ockhamn's razor (cheap on axioms, expensive with universes) would appear there as well. --Michael C. Price talk 11:31, 20 June 2006 (UTC)

My addition

Hi Michael,

Hi, it would be easier to follow your responses if you inserted in-line amongst the original text, rather than copying the original text and then commenting on it. In copying it you have failed to preserve the distinction between your text and my text when you lost the indentation. It is also recommended Wikipedia practice. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MDW: Can you point out to me which of my changes are needlessly repetitive?

MCP: It's already been pointed out that: And numbers 2, 3, and 4 say exactly the same thing.

MDW: I don't see that they say the exact same thing. If you want to combine 2, 3, and 4 together in one point because they are closely related, I have no problem with that.

That is already in the structure of the Advantages section. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MDW: Can you list the unverifiable assertions I made, and give me a chance to support them?

MCP: The very first clause is unverifiable (and I believe false): If Hugh Everett's theory was just another interpretation of Quantum Mechanics it would have no followers since almost any interpretation will have some followers. Do you accept that this is unverifiable? If you do then apply the same reasoning to the rest of your comments. If you don't then we have to debate it further. Which is it?

MDW: I think it is indisputable.

The you will have to provide a citation for it to go into the article. Same for any other beliefs you have that are not universally held by others. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

I can't believe you disagree with it. I disagree that almost any interpretation has some followers. Hugh Everett's theory started out having no followers aside from Hugh Everett. The only reason anyone accepted his interpretation is because it offers some advantages. Otherwise, it would be silly to accept an interpretation that predicts the existence of countless universes that can't ever be detected, and has no particular relevance for people living in our universe. Imagine if someone came along with another interpretation of GR, and this interpretation could never be verified, and did not make different predictions that could be tested. No physicist would favor such a theory. Do you really think otherwise? Why would any physicist favor such a theory?

MDW: Can you point out what you believe is not NPOV?

MCP: The same clause is also not NPOV for pretty much the same reasons.

MDW: Please explain. I don't see it. Whose point of view does my clause favor?

Your POV. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MDW: I think my addition contains a lot of information that is not in the article,

MCP: I disagree. I compared your text with what was there and I don't see anything new.

MDW: First, there are my quotes. Second, there is the fact that Everett left physics because of the poor reception his theory received.

Already in the Hugh Everett article:
He left physics after completing his Ph.D., discouraged at the lack of response to his theories from other physicists. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MCP: Remember there is a lot of implicit information that reader can access by linking through. A lot of my time has been spent updating the linked articles

MDW: Articles need to contain explicit information, readers should not have to figure-out relevant implicit information on their own.

I disagree (and so does Wikipedia) and I will revert verbose tracts that should be in other article. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MCP: such as: EPR paradox local quantum decoherence quantum measurement (now linked directly from "Advantages"), Schrödinger's cat wavefunction collapse (just added!) wave-particle duality and nested linked articles such as: Bell's theorem Bohmian mechanics correspondence principle counterfactual definiteness interpretation of quantum mechanics introduction to quantum mechanics quantum mechanics Universal wavefunction and many more so as to avoid cluttering up the MWI article. Which also improves Wikipedia generally -- as is intended -- which is why it is a Wiki policy, I believe.

MDW: Naturally, the article can't define every term, and spend time explaining extraneous material, but I think the average reader would want to see in the article everything I want to add. Can we invite some neutral readers here to get their opinion as to which version is clearer?

Ask the administrators whether they think their style guides should be followed. I know what I think they will say... --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MDW: Let's discuss this. . . .You are the expert on Hugh Everett's theory, not I. Can you reason with me? I am not a hard person to reason with.

MCP: Then start listening to the advice that people are giving you and STOP accusing them of attacking you.

MDW: I do listen to advice that people give me. But that does not mean I have to agree with every piece of advice people give me! I have a right to my own opinion, and to my own judgment. It sounds like you are saying I have to follow all the advice others give me. That is not reasonable. I never accused you of attacking me. Lethe has attacked me, and continues to attack me. Lethe is the only one I have a problem with.

Lethe does not attack you, he has reservations about the material you want to put into article; and so do I and others. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MCP: I believe part of the reaon why you (and others) like the FAQ is because it is clearly written and non-repetitive

MDW: Generally speaking people consider my writing to be clearly written and non-repetitive. John Nagel seemed to have liked my addition.

MCP: I once went on a business course called "effective writing" which was all about how to, well, write effectively.

MDW: I have probably had more writing classes than you. I am sorry you think my writing is amateurish. Most people I've encountered think the opposite. But we will get no where debating this highly subjective issue.

I refer you to the Wiki style guides, which emphasize conciseness and number of other writing points I have made. --Michael C. Price talk 18:01, 20 June 2006 (UTC)

MCP: The main points were the ones that I've already told you: don't repeat yourself (except in summaries and conclusions);

MDW: I don't believe I repeated myself at all! If I did, the repetitive portions need to be deleted.

MCP: less is more -- avoid verbosity, especially long discombobulating adjectives;

MDW: Thanks, until now I always thought excess verbiage and sesquipedalian adjectives were the hallmark of superior writing. Did you wonder why John Nagel thought my addition was "excellent" considering the fact in your estimation it was so poorly written, and so repetitive? I suspect others might find my addition superior to what exists. Three editors here disagree. I would like to hear more opinions. I will abide by the consensus. I didn't realize you held yourself out to be such an expert on writing style. I took many honors writing courses in a top learning institution, and was always a top student in my class. You have an excellent writing style. Perhaps, my addition needs to be reworked. But I am at a loss to understand your highly critical, school marmish tone here.

It was intended as a positive contribution. Since you don't care for my input on your writing style I shall say nothing more on the matter, except for the next comment... --Michael C. Price talk 18:37, 20 June 2006 (UTC)

I guess we humans were not all made the same, and were not always meant to see eye-to-eye. Let's focus on critiquing my addition.

....Your style affects the quality of your additions. Follow the wikipedia style guides or be reverted.
--Michael C. Price talk 18:37, 20 June 2006 (UTC)

MCP: provide only a few strong reasons rather than a mixture of strong and weak reasons.

MDW: I thought all the reasons I gave for MWI were strong reasons. Though, I beg to disagree with you. I think in an encyclopedic article all main reasons why proponents adhere to a theory should be given whether they are strong or weak. I suspect your absolute, categorical statement has some exceptions. Sometimes weak reasons can subtract from a case, sometimes they can add.

MCP: I believe we can all benefit from effective thinking. Try it and see.

MDW: Thanks, I never would have realized this on my own. Maybe, one of these days I will try effective thinking. It sounds so intimidating. In the meantime, I guess I will just have to muddle along with my trusty ol' ineffective thinking. I am so glad you have benefited from effective thinking. I promise to give it a try one of these days. Michael Price, you are one of the brightest people I know. We are not peers. You are countless orders of magnitude brighter than I. You are one of the most civil, patient people I know. I am at a loss to understand this highly pedantic, dress down. It is so not like you. I know I am not in your league, but give me some credit, and try to stay open-minded. I may not be the greatest writer in the world. I have never help myself out to be a great writer. But many people do find I present things in a clear and cogent fashion.

I would like to hear the opinion of average Wikipedia readers. I think you are operating at such a high level, with such an understanding of the subject, that you don't realize the average reader needs more explanation. The advanced physics graduate is not going to need as much explanation as the layman, but I think Wikipedia articles are supposed to be geared to the level of your average educated, literate reader, not the specialist. I think my addition is more comprehensible to the average reader than the existing version which is filled with countless, esoteric allusions understood only by a select group of illuminati.

Perhaps there is room for compromise on both sides.

Warm regards, Michael

Michael D. Wolok 16:26, 20 June 2006 (UTC)

The passive-aggressive sarcastic condescension mixed with flattery is quite unpleasant to read. You may want to adopt a more respectful tone. -lethe talk + 17:27, 20 June 2006 (UTC)
It is my belief that Michael D. Wolok's contributions to this article and talk page have been highly disruptive. Also looking at his recent contrbutions in WP, I just noticed that he has placed dozens of comments on WP user talk pages requesting assistance, suggesting he has been victimized by lethe. This suggestion is flat out ridiculous. If this behavior continues, other editors may have take another course of action, possibly beginning with an RfC. It's one thing to disagree with how the page is written, it's quite another to take the disagreement to the level of personal hostility that Wollok has. We simply cannot work in that environment.--CSTAR 18:57, 20 June 2006 (UTC)
Yes. Wolok's spamming campaign may have caused irreparable damage; User:HappyCamper reacted perhaps unwisely by reverting en masse Woloks requests, which has caused some community backlash and now HC may have left the project. My patience has ended. The RfC is being drafted. -lethe talk + 19:54, 20 June 2006 (UTC)

Non technical guide

We have two mutually exclusive views on how the MWI article should be written. Some people view MWI as a technical subject. Technical articles here are written to a very high, but usually accessible, level. Other people wish for a less technical article on the grounds, presumably, that MWI is of interest to a wider audience than other technical subjects (e.g. fourier transforms) usually are. And it seems there are very divergent writing styles involved as well. There doesn't seem much possibility of a meeting of minds between the two camps, so I suggest that non-tech's write their own MWI guide the way they wish, whilst the techs carry on with the exant article. Sound fair? There is already an introduction to quantum mechanics article. Type in "introduction to MWI" hit "Go" and you're off... --Michael C. Price talk 19:19, 20 June 2006 (UTC)

I have never liked the split as a solution to the problem of differing levels of technicality. Are you sure that we're not going to be able to meet all readers needs with one article? I am not at all convinced that we cannot. It's true that much of this article is currently completely inaccessible to the layman and the technical bits may even be hard for the physics student. But I don't know of any reason why this cannot be fixed. Certainly I haven't seen any serious attempts to fix it, so there's no reason to conclude that it's unfixable. For what it's worth, I never supported the introduction to quantum mechanics article and I think the end result of that split is an awkward article with multiple personality disorder. It is even less appropriate for lesser travelled topics like this one, though others may disagree. But let's see if we can fix before we do violence to this article. -lethe talk + 19:34, 20 June 2006 (UTC)
I'm not sure, but it's up to other people as well. But I certainly understand your concerns. FWIW I've suggested to Michael Wolok that he can import my FAQ as a skeleton to work around, if he wishes. --Michael C. Price talk 19:42, 20 June 2006 (UTC)
My own opinion is that this non-technical MWI guide is a bad idea and may actually violate WP policies and guidelines. I realize you are trying to be very accomodating with this gesture, but in the end, it may hurt more than help.
I am certainly not opposed to making the article more accessible. When I encountered the article two years ago it was a mishmash of different things. It had a reasonable intro but the rest of the article though it may have been "accessible" in some sense, had little technical content. I thought the easiest thing would be to delete some of the nonsense stuff and add something that showed the mathematical equivalence of several quantum dynamics formalisms, (1) the quantum operation formalism (which describes most general transformation the density matrix can undergo in an open system) and (2) the superposition over measurement histories formalism (3) The relative state formalism. I continue to get a lot of flack (ahem, even from you) that it was obscure and I admit it may very well be. That criticism is fair and I am certainly happy to see the article become more accessible even if it means obliterating my earlier contributions. But I don't think the solution is starting another introductory article: the result would be, in my opinion, an article with little "adult supervision" and one which would be deceptively accessible. --CSTAR 17:39, 21 June 2006 (UTC)
Have you considered moving/merging some of the partial trace & quantum operation formalism stuff into other articles such quantum decoherence, density matrix etc, which probably didn't exist a couple of years ago when you wrote it? There's some other stuff that might also be a candidate for moving, in particullar Denis's excellent "illustrative example" description which would add value to the Stern-Gerlach experiment. Of course we still need an overview of implications to MWI of them all in the MWI article. --Michael C. Price talk 19:51, 21 June 2006 (UTC)
Yes I think that's a good idea. --CSTAR 20:07, 21 June 2006 (UTC)
OK, I've started the ball rolling with a chunk on von Neumann & collapse, moved over to the wavefunction collapse (an easy decision). I'd like to find a better home for the Bloch spheres. Any suggestions? --Michael C. Price talk 23:21, 22 June 2006 (UTC)
Measurement I suppose, but the quantum measurement article is piss-poor. It's like sending the poor Bloch spheres to some Ring of Hell.--CSTAR 23:45, 22 June 2006 (UTC)
A cruel fate indeed. There must be something better for them, even if they end up with their own page. I guess we are trying database normalization. --Michael C. Price talk 01:05, 23 June 2006 (UTC)

Wolok RfC

I have filed an RfC about M. Wolok. Any interested parties are invited to comment. Some of the events occurring on this talk page are mentioned. -lethe talk + 14:25, 21 June 2006 (UTC)

In the interests of accuracy (& possibly pedantry) I should point out that I did not agree "to discuss line by line why the additions are unsuitable" but rather I only discussed them as so far as to make a point -- which meant on some issues (such as verifiability) that I did not get past the first sentence. To analyse further would have been repetitve. --Michael C. Price talk 16:28, 21 June 2006 (UTC)
I don't think Michael Wolok was being sarcastic and condescending past the first 2 or 3 sentences in his response to my writing suggestions. I suggest you delete the rest. Should you also mention my suggesion for a non-technical MWI guide, since it can be interpreted as a sort of mediation offer? --Michael C. Price talk 16:52, 21 June 2006 (UTC)
If you feel that my assessment was overly harsh or otherwise inaccurate, or would like to mention your other olive branch attempts with Wolok, please add a statement to the RfC. After this week's continued assaults from that quarter, I have become quite frustrated. I don't think I've ever lost my cool on Wikipedia the way I did here. -lethe talk + 19:08, 21 June 2006 (UTC)

Einstein on observation

It seems an age ago I said:

My understanding is that Einstein merely disliked CI's indeterminism, but that his fundamental objection was to having the role of observation hard-wired into the physics, instead of emerging from the physics. In a letter to Schrodinger I believe, although I'd have to check. But Einstein died before Everett published so how he would have reacted to MWI is conjectural.--Michael C Price 09:30, 25 May 2006 (UTC)

I finally found it; it was to Heisenberg, not Schrodinger, and I've added it to Wikiquotes.

"Whether you can observe a thing or not depends on the theory which you use. It is the theory which decides what can be observed." Albert Einstein to Werner Heisenberg, objecting to placing observables at the heart of the new quantum mechanics, during Heisenberg's 1926 lecture at Berlin; related by Heisenberg in 1968, quoted by Abdus Salam, Unification of Fundamental Forces, Cambridge University Press (1990) ISBN 0521371406, pp 98-101

--Michael C. Price talk 23:05, 23 June 2006 (UTC)


I hate to quibble. However, I have quite a big quibble with this article at the moment. So far as I am aware, and that lovely book Princeton spewed out in 1973 seems to agree with me, the MWI and the relative state formulation are not semantically identical. To wit, Everett devised a theory of a universal wavefunction, which can be mathematically expressed using the relative state formulation. Then, other people (Graham, DeWitt, Wheeler) came along, and interpreted Everett's relative state formulation in different ways: they decided what the (meta)physical implications of the mathematical formalism would be. The Many Minds Interpretation also uses the same mathematical machinery, with different interpretative features. And what about "bare theory"? That simply isn't mentioned at all, and yet it, too, uses Everett's formulation.

What I am saying is that the MWI is neither the only nor an inevitable consequence of Everett's work, and Everett himself didn't come up with it: it was added after the fact to his work, by Wheeler et al. Surely the article should reflect this? And would it not perhaps be better to have a separate article on the formulation itself, to which the Many Minds Interpretation can refer, and if at some point an article on bare theory is written (I might do it myself), it too can refer to that? Byrgenwulf 15:04, 27 July 2006 (UTC)

Everett didn't just churn out a mathematical formalism, he also made a foundational metaphysical assumption, that the universal wavefunction was the "basic physical entity". So already, armed with just this knowledge and the absence of wavefunction collapse in Everett's theory, it is hard to see how Everett could not believe in the existence of alternative histories or parallel universes - what DeWitt called "other worlds". But we don't have to wonder, Everett also taked about the observer "branching" and splitting as a result of a measurement in the DeWitt-Graham book; these are differences in emphasis and presentation only. (I also have anecdotal evidence from conversations with Deutsch, who had met Everett, who described Everett as the most "extreme many-worlder possible", but I guess this is not (quite rightly) admissible. But I'd thought I'd mention it anyway.)
Consider this from statement from one of Everett's associates[1]:
"Atheist or not, Everett firmly believed that his many-worlds theory guaranteed him immortality: His consciousness, he argued, is bound at each branching to follow whatever path does not lead to death —and so on ad infinitum. (Sadly, Everett's daughter Liz, in her later suicide note, said she was going to a parallel universe to be with her father. [149a])"
--Michael C. Price talk 15:58, 27 July 2006 (UTC)
I never said he didn't believe in it (although I found the story of his daughter interesting - thanks)! My point is that the MWI does not follow inevitably or exclusively from the relative state formulation itself. For example, the bare theory uses the fact that Everett disposed of collapse dynamics, but still has an eigenstate/eigenvalue aspect to it. Similarly with the Gell-Mann and Hartle reading, which doesn't make use of many-worlds at all...and, of course, many-minds.
So, while the article could mention that Everett believed in the MWI, that interpretation, so far as I remember, was first clearly set forward by DeWitt in 1971. The mathematics underlying it had been around since 1957 (once again, if I remember correctly - somewhere around then!) - even if Everett had believed in many worlds beforehand, it doesn't matter, because the formulation is not the interpretation. The bottom line is that the relative state formulation refers to the manner in which Everett formulated quantum mechanics without wave collapse (the spinoff of the universal wavefunction being the "fundamental reality"), while the MWI is one of many ways in which that formulation can be related back to some form of intuitive understanding of what it implies. Byrgenwulf 16:25, 27 July 2006 (UTC)
OK, Everett's beliefs are irrelevant. But the relative state formulation, as initially published in 1957, assigned reality to the entire universal wavefunction and hence to each component of each and every possible decomposition or superposition. Ergo each quantum "alternative" is real. Looking at all other no-collapse interpretations they have to avoid this conclusion by either:
1) not assigning reality to the wavefunction (Bohm doesn't, Gell-Mann etc are agnostic)
2) adding new metaphysical assumption(s) (e.g many-minds)
--Michael C. Price talk 18:11, 27 July 2006 (UTC)
Other than bare theory. The problem with bare theory is that if it were true, we would have no way of proving it (but then that's common to many theories in this genre!). I don't personally put much stock in bare theory, but it is "there".
I think that adding extra worlds/universes/whatever also counts as a "metaphysical assumption". However, this is probably not the place for these sorts of discussions (not that they're not fun). The bottom line still is that the relative state formulation and MWI are simply not the same thing.
I don't agree. You seem to equate "the maths" = "bare theory" = "no interpretation" which is fine, but I am pointing out that RSI = "bare theory" + "a metaphysical assumption". Until we settle that we are not going to agree about much else. --Michael C. Price talk 18:49, 27 July 2006 (UTC)
How about this. We have an article on Many Minds (but it could do with improvement). Once I'm finished RQM I'll start one on bare theory (which anyone can add to, of course). Then, we tease out some things from this one (MWI) and make a relative state formulation article, which focuses on the actual mathematical formulation of the theory, targeted at people with a more technical background. One of the concerns with the current article gaining Featured Article status was that it seemed far too technical to some. Of course, mathematical/formal analyses of the various interpretations can and should be included in individual articles on them, but the heavy stuff can be included in the relative state article (which also gives more room for covering Everett's proof of the formulation, etc.). Also an article on philosophical implications and so forth. We then create an infobox for a "series on the relative state formulation" which includes all the various articles related to it.
What say you? Not a small project, but could be very worthwhile, especially since this particular "genre" of interpretations is rapidly overtaking Copenhagen as the "seminal" one, and is of immense interest to both physicists and the layperson. Byrgenwulf 18:29, 27 July 2006 (UTC)
I'm not sure that we can meaningfully separate MWI from the RSI for the reasons I've already outlined. Let's settle that first and then see we were we are. As for the state of the MWI article, I am also unhappy with the clarity of technical presentation of some sections and I am working (slowly!) on a private copy of some parts. Splitting it up into separate articles, or at least shifting chunks to more appropriate articles, is definitely a good thing. Some stuff has already migrated to better homes. --Michael C. Price talk 18:49, 27 July 2006 (UTC)

Could someone give a quick explanation

Is the many-worlds interepretation really saying that there are infinite universes branching off from this one? How does this solve the deterministic probelms of quantum physics? And second of all, is there actually any proof for the idea of paralell universes? Is this the same as multiverse theory? I noticed in the multiverse theory article that there are many critiques of it. How come this version is so popular? It sounds like pure junk science to me.

Quick explanation: MWI accepts the reality of multiple outcomes at all levels (gluons to galaxies), not just at the microscopic level. The big picture, with all multiple outcomes, is determinate. The proof of MWI is that all other interpretations are garbage for one reason or another. The multiverse is more philosophical, less grounded in empiricism than the MWI. It is popular for the reasons outlined in the last two (or possibly three) sentences. Please specify which part sounds like junk. --Michael C. Price talk 00:03, 9 August 2006 (UTC)

And another thing, if this is true, do paralell universes branch off only when a sentient being is present? I once read in a very popular science fiction novel, Hominids, that humans are the only species that has free will, and every one of their actions creates seperate paralell universes. Non-sentient beings and objects etc. follow entirally deterministic paths and only humans can break the chain. I'm not sure how much basis this idea has- the guy who wrote it, Robert J. Sawyer, has done alot of research into quantum physics, but I'm not sure. Could someone explain?

Complete garbage: you did want a quick explanation, right? Branching is a consequence of thermodynamics, not sentience.  :-) --Michael C. Price talk 00:05, 9 August 2006 (UTC)

Whoa, I don't know what happened. When I was talking to you on the disscusion section of Many-Worlds Interpretation, every time I saved my reply the page reloaded as an entirally different talk section, I have no idea what that was. Still, here's my reply:

"Yeah, sorry I brought that thing about Sawyer up. It's probably just a theory of his, but thanks so much for replying so quickly. I have a number of other questions, and the reason why I said it sounds like garbage is because to me, it implied the idea of constantly branching off paralell universes. Still, I don't think you were clear if that's what MWI implies, and I'd like more clarification on that.

Here are some of my other questions- if MWI implies paralell, branching universes, as seen by this page written by a writer for Scientific American:

Does this imply that their are infinite copies of us in infinite universes or what? This part caught my eye in the FAQ section:

"Multiverse ethics From Gerald, Oct 5, 2003, 14:31 Q: Doesn't the multiverse theory completely trivialize existence? It puts the burden for individual responsibility on the shoulders of the universe. Why do anything? If you decide to be a lazy slug, that just means that your particle clone elsewhere will be the one who wins the Nobel prize. And vice versa. Similar destructive arguments can be applied to morality. If the theory is correct, "wrongdoing" doesn't exist. Ultimately I've realized one almost has to believe in fantasies, in theories that only could be possible but probably aren't. Otherwise, one cannot make meaningful decisions to advance their own survival or to aid anyone else. A: I'm not convinced that the existence of parallel universes implies that I should dramatically alter my behavior. Yes, some near-clones of me indeed win the Nobel prize, but only a very small fraction of them! As in the gas station question above, it's important to keep track of the statistics, since even if everything conceivable happens somewhere, really freak events happen rarely, in an exponentially small fraction of all parallel universes. It's these statistics that make existence complex and interesting rather than trivial. "

Of course, I can't tell if hes pushing multiverse theory, something similar to the pure science fiction theory Sawyer wrote about, or MWI. There's also this BBC page:

Is the BBC's explanation speaking of MWI or multiverse, or something else entirally? I've heard of paralell universe theories before, but I just brushed them off. Still, right now, I'm very intrigued and I'd like an explanation."

The BBC account is mixing up MWI, the multiverse and M-theory -- so it really is pretty confused. To answer an earlier point, yes MWI implies branching timelines or histories (although whether a truely infnite number or just very, very large is debatable). I'm glad you're asking these questions -- it makes me realise how deficient the MWI wikipedia article is. This is slightly egotistical of me, but your might find this Everett FAQ useful. --Michael C. Price talk 00:34, 9 August 2006 (UTC)

Oh, well thanks! Still, is what the BBC article says about the whole thing about, well, universes colliding accurate? I've honestly never heard of anything like that before. Second, when you say "molecular level", does this mean that universes that branch off have differences so miniscule to this one that they can only be seen on the molecular level? Also, like that one page I linked relating to Scientific American, are most paralell universes very similar to our own or what? I know what you said about that being very debatable, but the man who wrote it has written for Scientific American a number of times, so I'd say he's rather credible.

And one last thing- is there a branching timeline for every little thing in this universe, and the same going for each branching timeline that comes from this one?

The colliding thing comes from M- or string theory or some TOE -- not relevant to MWI, which is purely a nonrelativistic quantum effect. Yes to your molecular level question. Most parallel universes in MWI will be very very different from ours -- but there're an infinite, or near infinite, number of them in total , so even a relativity small number of "near" neighbours is still a very very large number. By the SciAm guy I take it you mean Max Tegmark -- he knows what he's taking about -- but he covers the multiverse more, which is a much more general concept than just MWI. Yes and yes to your final sentence. --Michael C. Price talk 00:51, 9 August 2006 (UTC)

Thanks, I'm almost done here. A few more questions:

Is the collision thing even true? I've studied a number of ideas of how the big bang came to be, but I've never heard of this. It seems like the BBC article just mentions a handful of scientists, probably a minority, who hold this theory to make the article more bizzare.

I'm sorry to be a bother again about it, but I still don't think you were clear about whether or not most branching universes are similar, almost identical to our own. Second of all, how can it be this precise? It seems to be a paradox, since for every branching universe, there's an infinite number or extremely large amount of universes for each single branching one, if that's what you're getting at. The only way this couldn't be true is if this is the original universe of our's, unless we're just one of the many branches of an original universe. And do our copies in the other branching universes have sentience as we do, or what? Can anybody be certain of these?

As I said, the collison thing has nothing to do with MWI. More to do with the ekpyrotic or Brane cosmology if you want a link (neither of which if true would have any impact on MWI). Perhaps I see where you're coming from with the branching thing -- universes which branch off are almost identical but as time passes they diverge more and more. So ones that diverged from "ours" a nanosecond ago are pretty similar, whereas ones that diverged a billion years ago are very very different. You're are right that "we're just one of the many branches of an original universe" (except that if eternal inflation is correct there may be no "original".... but I don't really want to go there). As for "And do our copies in the other branching universes have sentience as we do, or what?", well if they don't it would violate one or two rather fundamental scientific principles and imply vitalism -- which is not mainstream. BTW you have hit the nail on the head with your question about how to make branching precise -- since it is based on quantum thermodynamics it is inherently fuzzy -- but thermodynamics admits to no easy explanation, so that's another topic I don't want to discuss here (my FAQ covers it to some extent) --Michael C. Price talk 01:20, 9 August 2006 (UTC)

Ah, I think I'm getting it now, thanks for clarifying. Maybe this conversation can be applied to the main article. But still, just a few more questions- is MWI and paralell universe theory one in the same? Was there an original big bang of this universe, this timeline or whatever, and was it this one specifically? Or is this the original universe that all the other divergent timelines branched off of? Or am I just getting on to eternal inflation? I checked the link on eternal inflation but it just leads to cosmic inflation and makes no mention of anything about eternal. Does that have to do with the idea that this universe is one of many in a chain of previously existing universes, and when it collapses, another big bang occurs?

So what I'm getting at about the divergent timelines is this- say for example, there was a big bang that created another universe. Going in accordance with MWI, numerous other timelines of big bangs must have branched off from this one. Would these multiple divergent timelines result in drastically different universes? Is our universe a continuation of big bang, and if so, when another divergent timeline occurs, does it just pop off from the other one?

As I said earlier, MWI is the outcome or consequence of non-relativistic quantum mechanics and is really quite agnostic on cosmological questions about the big bang and such like. All events are handled within MWI, big bang or no big bang. (BTW eternal inflation does talk about eternal inflation -- eventually.) I'm a bit worried about your question "Or is this the original universe that all the other divergent timelines branched off of?": there is no "original universe" in this sense around today, any more than any of your cells are the original fertilised ovum. The timelines/histories/worlds/universes split or divide or branch or fork. I'm turning in for now, so read the links and we'll resume later. --Michael C. Price talk 02:02, 9 August 2006 (UTC)

Hey, I'd like to thank you again for answering alot of my questions. I don't see why you'd be worried about the "idea of an original universe"- it's a legitimate question and I feel its justifiable considering how vague this article is. No offense though. But seriously, I see this as a problem with many articles on physics on wikipedia. Far too many of them are filled with complex, abstract language that the majority of people would have a hard time even grasping, not to mention all of the mathematical equations. Still, you've been great help, but since this way communicating is abit slow, I guess I should take this conversation to a physics professor at a nearby college or something. Still, I have one more question. The BBC article mentioned these people in paralell universes existing mere milimeters away, yet existing still in completely different universes. Tegmark's FAQ mentioned this, but he was very vague on whether this was true or not. So is the milimeters away thing true or not? And was the BBC's mention of it completely unrelated to MWI?

The millimetres things is a reference to the conjectured dimensions of the "bulk" at brane cosmology (an unproven hypothesis, hence Tegmark's vagueness) but more importantly has nothing to do with MWI. On the "original universe" point did my "ovum" analogy help? --Michael C. Price talk 09:08, 9 August 2006 (UTC)
BTW, good luck with the physics professor approach -- my guess is they'll have to be real friendly to answer coherently. And I do appreciate your questions because, as I said, they make me realise the deficiencies in the article. --Michael C. Price talk 09:22, 9 August 2006 (UTC)

Yes, yes it did. It's extremely late where I'm at but I have one more question that to me seems like a paradox with MWI. Tegmark, in his FAQ section, gets a question about MWI trivializing existence, and he mentions how only a very small amount of universes would have him winning the nobel prize. However, this is how my question goes. We take the current universe, where Tegmark is a regular scientist that writers for SciAm. Then, we jump to one of the rare universes, where Tegmark wins the nobel prize. However, which universe has multiple paralells that branch off from? This one, or one of the rare universes that Tegmark wins the nobel prize?

They all branch endlessly. Each universe is equally real, although some occur "more often" than others (in a way that relates to probability). --Michael C. Price talk 10:58, 9 August 2006 (UTC)

Second of all, which of these universes came first? And when another paralell universe comes into existence, does it just pop into existence?

No, a universe splits or branches. This splitting is not instaneous either but spreads causally. See Schrodinger's cat. First the radioactive atom splits, then the cat, then the external observer etc etc. --Michael C. Price talk 10:58, 9 August 2006 (UTC)

If our universe popped into existence from another one, does this mean all the history, the timeline we see is just an illusion?

No, see above. --Michael C. Price talk 10:58, 9 August 2006 (UTC)

That's what I was trying to get at about which universe came first by the way. It seems almost paradoxal and sounds similar, almost like another Schrodinger's Cat if I'm not mistaken.

Exactly so. --Michael C. Price talk 10:58, 9 August 2006 (UTC)

And one last thing, are proponents of MWI sure there are infinite or finite branching universes?

Unsure. See previous responses. --Michael C. Price talk 10:58, 9 August 2006 (UTC)

Ah, so does MWI run into a whole new set problems even after supposedly resolving Schrodinger's Cat?

No, not at all. Observational cosmology is not a finished science (and how could it be?), that's all. Don't confuse statements of observational incompleteness for deficiencies in a theory. --Michael C. Price talk 11:08, 9 August 2006 (UTC)

And this is a bit of a personal question, but like Tegmark was asked, do you feel MWI trivializes existence at all?

No, see my FAQ. --Michael C. Price talk 11:08, 9 August 2006 (UTC)

Well thanks alot for answering my questions. I guess this is my first real look into quantum mechanics and it feels like there's no turning back, and you've been extremely helpful. Thanks again! And by the way, where do you mention in your FAQ about the trivialization of existence?

Q24 Does many-worlds allow free-will? --Michael C. Price talk 01:10, 20 September 2006 (UTC)


Reading the Cat articles makes it clear why I never heard any serious discussion of "Interpretation of QM" while I was in school or doing basic research (in junior positions) at great research centers. It was all perfectly clear to him in 1935, except that he didn't know how to answer the EPR paradox, which was contrived to be contra-intuitive. The discoverers of QM already knew what they were doing, just as Einstain did about relativity. It is just that it takes a century for these things to filter down.

I repeat here that the main difficulties seem to arise when people re-phase what they have read or heard in ordinary language. Since QM cannot be expressed in ordinary language, this is like the game of "telephone", in which people sitting around a table each whisper what they heard from the person on the other side. It is worse because the fact that QM disagrees with ordinary language systematically favors more classical views. If you go back to someone like Schrödinger (or Weinberg) who knows QM well, the picture is much clearer. I admit that when I first came to Wikipedia I did not realize that people with the standing of Roger Penrose had questions about basic QM. However I still believe that worrying about these things is (professioanally) a minority point of view. As far as I am concerned, it was all settled in 1935, except that the "many worlds" predication for EPR experiments had not yet been confirmed. (As a result of this, Schrödinger suggests and argues against hidden variables ideas that have now been ruled out, as explanations, by experiment.) David R. Ingham 04:24, 9 September 2006 (UTC)

Recent edit on Schrödinger's cat article

The following edit requires a less telegraphic style:

It resembles a return to the concepts of the 1935 Schrödinger's cat article.

The intent of this statement (I believe) is to that the state of the cat (before it is observed) is a quantum superposition of two histories. This requires more elaboration and probably shouldn't be in the intro. BTW, there are several more "animal friendly versions" of Schroedinger's cat. One due to Henry Stapp (somebody climbs up or down some steps based on an experiment's outcome) and another due to Peter Forrest who uses some kind of stuffed animal in place of a real cat. --CSTAR 16:41, 10 September 2006 (UTC)

I've removed the statement: it's opaque and implies that Schrodinger had some sympathy with MWI. I don't believe that any of the founding fathers of QM ever expressed any such view, perhaps because they were too old or dead by 1957. --Michael C. Price talk 01:16, 20 September 2006 (UTC)


I'm unhappy about dragging Schrödinger's cat into it until someone defines a cat, "alive" and "dead" in terms that the quantum formalism deals with (multiparticle Hamiltonians, etc). Von Neumann said to someone who questioned whether a machine could think: "You tell me *exactly* what you mean by think, and I will design a machine that can do it". In this statement, replace "think" by "cat", "alive", "dead" and even "conscious"...

If it's testable then it's not an interpretation (though you have to specify who it's testable by, since an observer forks). And if it's an interpretation then it's a matter of taste. Here are three things which I find in bad taste about Many Worlds:

1. The dynamics is time-reversible, but MW's forking of the worlds defines an arrow of time. (If this is the origin of the arrow of time we perceive, can any MW adherent show it? Analogy is not an argument!)

2. For a discrete eigenspectrum of the operator corresponding to the observable being measured, many-worlds says there is one world branch for each possibility. What do you do when the eigenspectrum includes a continuum?

3. Consider the experiment in which I put a beam of electrons (in silver atom orbitals, as usual) into a Stern-Gerlach apparatus. It divides into two beams. Discard one beam and put the other through a second SG apparatus oriented differently from the first. The output is again two beams. I want to know into which of these beams the next electron to enter the second SG apparatus will go. Quantum mechanics gives the ratio of intensities of the two output beams in terms of the angle between the SG apparati, but cannot be more specific. Yet this is a well-defined experimental issue. Many Worlds is an intellectual valium that rationalises my inability to answer. (Copenhagen simply censors my question without intellectual valium.) It is fine for farmers and bankers not to care about such things, but the job of theoretical physicists is to ask such questions, and if you are not prepared to ask questions then you'll never get answers (unless you stumble upon them by accident and recognise them for what they are). I will gladly accept a reason WHY we cannot answer, but we do not even have that - AG, Stockport, UK.

1. It is the initial conditions that determine the arrow of time, not the CPT reversibility of the equations of physics.
2. A continuous eigenvalue spectrum implies a continuum of resulting worlds after a measurement. This is not a problem with the theory.
3. The electron "goes into" both beams, but into different beams in different worlds. --Michael C. Price talk 01:07, 20 September 2006 (UTC)

Thank you. Re (2), what does "a continuum of resulting worlds" mean, please? Re (3), I do not experience myself splitting when I do a measurement, so there is a well-defined "I". It is this "I" who (still) wants to know into which beam the next electron will go. As a further point (4), nobody knows whether tomorrow I will crash my car or not, yet we do not suggest that the universe splits into two accordingly - what is the difference betwen this and electrons; where and how is any boundary of applicability of MW drawn? And (5) a "measurement" - which is where the split into MWs is held to take place - is really just an interaction governed by the quantum evolution equation for the joint system of observer-plus-observed. On that view there is no splitting. Precisely when and how does the split take place? - AG, Stockport, UK.

Sadly I don't have time to give full answers: may I suggest that you read an FAQ I wrote some years ago on the subject? But briefly, (4) there is no boundary between electrons and elephants or gluons and galaxies; MWI says that you will both crash your car tomorrow and not crash it. (5) is covered in the FAQ. (3) was an issue orginally raised by Everett: the laws of physics do not allow yourself to be aware of your splitting, anymore than you are aware of your motion around the sun. The latter does not cause us to reject heliocentricism, the former should not cause us to reject many-worlds. On (2) the continuum of outcomes issue, I fear no simple answer comes to hand, although Everett does point out that any branching process is ultimately limited by the entropy of the observer(s)'s memory (which is presumably finite). --Michael C. Price talk 18:39, 20 September 2006 (UTC)

You say that MW should also be applied to macroscopic events. Either I will or won't win the lottery tomorrow and it is determined by the motion of the balls in the urn, which obey the laws of physics but are too complicated for me to follow. The reason I don't know is my lack of information about the balls. But someone else might ingeniously have fixed it so that he does know. You would say there is a split in my case but not in his case - but we are talking about the same event. Contradiction. So MW cannot be applied to macroscopic events. If you say it can be applied to microscopic ones, how and where do you draw the border? - AG, Stockport, UK.

But the balls in the urn are also subject to quantum indeterminancy and chaotic amplification, so the alternatives (win/lose) are quantum alternatives, not just classical alternatives. Same with crashing/not crashing your car tomorrow. As such MWI says there really is a world-split over the outcomes. (Of course there are many different ways of losing/crashing etc, but that does not change the principle. And there are classical events (such as whether a giant asteroid strike will destroy the Earth tomorrow) which are probably best viewed outside the MWI paradigm.) --Michael C. Price talk 20:44, 20 September 2006 (UTC)

Thank you. How do you draw the line between what you call classical events and those to which MW applies? Where is the conceptual difference between car crashes and asteroid strikes, please? - AG, Stockport, UK.

There isn't a conceptual difference, it's just a matter of degree and the extent of the time frame over which the question is posed. Any and every event has a quantum origin, if we look back far enough; it's just a question of how far we are looking back or forward. A car crash tomorrow is a quantum event because it will depend on an earlier sequence of neuronal firing that was probably dependent on quantal processes. For a car crash in the next 5 seconds, the die has already been cast and is no longer a quantum event, in the sense no other outcome is now possible. For a giant Earth-asteroid collision the die was cast back over a much longer period (probably millions of years); i.e. for an asteriod collision tomorrow the branching has already happened and we can analyse this classically, for a car crash tomorrow the branching has not yet occured and must be handled quantally (i.e. within the MWI framework). --Michael C. Price talk 22:15, 20 September 2006 (UTC)

Thank you, but I find this unconvincing. You are still saying that some events should be viewed as inevitable and MWI is not applicable to these, and that some events are undecided so that MWI applies. I want a clear criterion such that if I quote a well-defined experiment and timescale, I know whether MWI applies. Without this I can assert that MWI does not apply to anything and you cannot refute me! - AG, Stockport, UK.

There are many fuzzy but valid concepts in physics: entropy, decoherence and Everett branching are some of them. Where does outer space begin? Yet there is an outer space. etc etc --Michael C. Price talk 23:58, 20 September 2006 (UTC)

Nobody needs to define a border between "outer space" and closer regions in order to do physics. Because there isn't a consensus about entropy doesn't mean that there isn't a well-defined concept involved. One school might well have the answers, but after so much confusion it would take a generation to clear up. (I have my own preferences.) But it is specifically MW I am seeking clarity on, which I think is reasonable on its own Wikipedia discussion page. You have said that some events should be viewed as inevitable and MWI is not applicable to these, and that some events are undecided so that MWI applies. I request a criterion that I can apply to a well-defined experiment and timescale that will tell me whether or not MWI applies. Otherwise I can assert that MWI does not apply to anything and nobody can deny it. This is emphatic writing, so let me assure you - nothing personal. Please also tell me which of your FAQ nos. deals with my query (5) above. - AG, Stockport, UK.

OK, I see the problem; this isn't an issue about many-worlds, it's a question of where the classical-quantum divide exists, if it exists as at all (which it doesn't). It was a mistake of mine to attempt to draw a distinction between classical and quantum events. Every event is a quantum event since all of classical mechanics is subset of quantum physics -- it's just that in some circumstances we can take the more simplified classical approach as sufficient to explain what's going on, whilst keeping in the back of our minds that the full-blown quantum analysis (which would involve a MWI approach) could also be applied.
Question 5 was about Everett splitting. This is covered in the FAQ by :
Q5 What is a measurement?
Q6 Why do worlds split? What is decoherence?
Q7 When do worlds split?
Q8 When does Schrodinger's cat split?
Q17 Why don't worlds fuse, as well as split? Do splitting worlds imply irreversible physics?
--Michael C. Price talk 19:14, 21 September 2006 (UTC)

Thanks for the reference. I do mean this to be about many-worlds - I was using the difficulty in defining the classical/quantum border as part of an argument against MW. Let me persist: nuclear events such as radioactive decay can be arranged to have macroscopic consequences, via Schrödinger's-cat type arrangements. When then is MWI to be applied and when not? You wrote that an asteroid crash was not subject to MW-splitting but whether my car crashes tomorrow is. Without a criterion for when MW applies, it is either applicable to everything or nothing. If it's applicable to everything then I can easily set up a situation in which person A doesn't know what will happen and says there will be a split corresponding to the possibilities, but person B has more information about the system and knows the outcome, and says there is no MW split. (Person B might simply have bribed the system operator.) So A and B disagree about whether there is an MW split. Splitting either happens or does not; it is not in the eye of the beholder - so this is a contradiction. So MW isn't applicable to everything. So (because of the absence of an applicability criterion) it is applicable to nothing... - AG, Stockport.

MW / QM is applicable to everything but, as I've said in a number of ways, sometimes other ways of analysing the situation are more appropriate (= simpler). Crashing your car tomorrow involves QM (and hence MW) since it will depend on quantal events such as the pattern of neuronal firing tomorrow. The probability of a giant asteroid colliding head on with the Earth tomorrow can be calculated with just Newtonian mechanics -- the outcome is not sensitive to any further microdetails. Or look at it another way, the MW-splitting associated with the asteroid strike/no strike has already happened (probably millions of years ago). --Michael C. Price talk 21:41, 21 September 2006 (UTC)

I couldn't agree more that "sometimes other ways of analysing the situation are more appropriate (= simpler)"! I'd say every time. If you think that MW helps in looking at radioactive decay (for instance), which is something nobody knows how to predict, please outline what it helps and why. It's an interpretation so we can't appeal to experiment. Personally I don't find it helpful. What am I missing? - AG, Stockport.

Sure it's interpretational, which is why I have no problems with calling it MWI, although MW-"metatheory" is probably more accurate. AFAICS MWI is the only interpretation of quantum mechanics that gives us a scientific model of reality. This is particularly useful in the observer observed problem. --Michael C. Price talk 23:25, 21 September 2006 (UTC)

The section on "Speculative Implications" currently says:

...It involves a quantum suicide machine and an experimenter willing to risk death. However, at best, this would only decide the issue for the experimenter; bystanders would learn nothing.

Actually, if the quantum suicide approach actually worked, it would place the subject in a world where both he and bystanders had witnessed the success. Although the results would not be reproducible with other subjects, this apparent "non-reproducibility" is properly predicted by the theory. With enough repetitions of the experiment, even the most skeptical bystanders ought to be convinced. Unfortunately, it would leave an awful lot of corpses in other worlds.

Thread continued from Introduction to quantum mechanics

This page seems to be the category for Schrödinger's views of how to interpret his own theory (at one time).

Wave function collapse (again)
In general, I am happily surprised by the present state of this article [Introduction to quantum mechanics], but somehow "Schrödinger's equation then fails" has come back. As he said in his "Cat" article in 1935, what happens is that the system needs to be described by the many-body form of the equation. I will try a simple fix, but others also should work on making it both correct and understandable. David R. Ingham 01:23, 15 October 2006 (UTC)
Two points:
1) Wavefunction collapse does not mean that the entity becomes "particle-like", as is currently implied. If you are measuring wavelength then the reverse occurs, namely a particular frequency is selected (as happens when a radio detector is tuned to a single frequency).
2) Where does Schrödinger's 1935 "Cat" article state that wavefunction collapse is successfully modeled by the many-particle picture? I can't find such a statement. --Michael C. Price talk 08:06, 15 October 2006 (UTC)
He didn't say one can calculate an observation purely with QM. There are too many variables. But he anticipated, as has since been observed, that when you "shut up and calculate" QM never "fails". The problems like EPR only arise when classical intuition is involved. Any useful "interpretation" must deal with this. David R. Ingham 15:38, 16 October 2006 (UTC)
But what section of the article does he say this in? --Michael C. Price talk 16:34, 16 October 2006 (UTC)
I will look back if I have time. The article is worth re-reading. He does say that the only discontinuity is a mental one, but I don't remember the words. This is not really the place to discuss this because the fact that we disagree shows that it is an advanced topic.... David R. Ingham 22:16, 16 October 2006 (UTC)

This is mostly is in 10. Theory of Measurement, Part Two of Some quotes

Things are not at all simple. It is the most difficult and most interesting point of the theory. Obviously we must try to comprehend objectively the interaction between measured object and measuring instrument. To that end we must lay out a few very abstract considerations.
The insufficiency of the psi-function as model replacement rests solely on the fact that one doesn't always have it.
Now how do things stand, after automatically completed measurement? We possess, afterwards same as before, a maximal expectation-catalog for the total system. The recorded measurement result is of course not included therein. As to the instrument the catalog is far from complete, telling us nothing at all about where the recording pen left its trace. (Remember that poisoned cat!) What this amounts to is that our knowledge has evaporated into conditional statements: if the mark is at line 1, then things are thus and so for the measured object, if it is at line 2, then such and such, if at 3, then a third, etc. Now has the psi-function of the measured object made a leap? Has it developed further in accord with natural law (in accord with the partial differential equation)? No to both questions. It is no more. It has become snarled up, in accord with the causal law of the combined psi-function, with that of the measuring instrument. The expectation-catalog of the object has split into a conditional disjunction of expectation-catalogs - like a Baedeker that one has taken apart in the proper manner. Along with each section there is given also the probability that it proves correct - transcribed from the original expectation-catalog of the object. But which one proves right - which section of the Baedeker should guide the ongoing journey - that can be determined only by actual inspection of the record.
What have we won by this analysis? First, the insight into the disjunctive splitting of the expectation-catalog, which still takes place quite continuously and is brought about through embedment in a combined catalog for instrument and object. From this amalgamation the object can again be separated out only by the living subject actually taking cognizance of the result of the measurement. Some time or other this must happen if that which has gone on is actually to be called a measurement - however dear to our hearts is was to prepare the process throughout as objectively as possible. And that is the second insight we have won: not until this inspection, which determines the disjunction, does anything discontinuous, or leaping, take place. One is inclined to call this a mental action, for the object is already out of touch, is no longer physically affected: what befalls it is already past. But it would not be quite right to say that the psi-function of the object which changes otherwise according to a partial differential equation, independent of the observer, should now change leap-fashion because of a mental act. For it had disappeared, it was no more. Whatever is not, no more can it change. It is born anew, is reconstituted, is separated out from the entangled knowledge that one has, through an act of perception, which as a matter of fact is not a physical effect on the measured object. From the form in which the psi-function was last known, to the new in which it reappears, runs no continuous road - it ran indeed through annihilation. Contrasting the two forms, the thing looks like a leap. In truth something of importance happens in between, namely the influence of the two bodies on each other, during which the object possessed no private expectation-catalog nor had any claim thereunto, because it was not independent.

This last quote is a whopper, but I read it partially to say that one loses track, not because of any change in the applicable physical laws, but because, I said above, there are too many variables to continue the quantum description beyond the part of the experiment which was designed to be describable and soluble with QM.

David R. Ingham 20:48, 22 October 2006 (UTC)

Thanks for the pointer, but this is not the place to discuss, at great length, Schrodinger's views on QM. Perhaps the talks pages atdecoherence or interpretation of quantum mechanics? --Michael C. Price talk 21:08, 22 October 2006 (UTC)

I picked this place because, of the categories of interpretations that Penrose listed in The Road to Reality, this is the one that appeared to be closest to Schrödinger's views, which are similar to those I learned from sources like Messiah. (Though Schrödinger did not consider the question closed at that time.) Also, I have had trouble trying to change Interpretation..., single handedly, to make the views I have always considered standard, and I now realize are so old, clearly visible there. David R. Ingham 00:28, 23 October 2006 (UTC)