# Many Worlds Theory

1. ### Actuality

8
Hello,

I am new to this forum. This is an excellent, informative forum; therefore, I felt compelled to join.

I would be interested to engage in dialogue with individuals who support the Many-Worlds interpretation of Quantum Theory. Personally, I despise this interpretation as I believe it is preposterous. I much prefer the Copenhagen interpretation.

Last edited: Mar 25, 2012

Stuff like"many worlds"? Descriptions such as codswallop come to mind.

3. ### JamesOrland

93
Well I am a supporter of the many-worlds theory :P

And terms like 'codswallop' and 'preposterous' sound a little bit harsh, and not very technical, let's avoid the use of them, shall we?

So, let's start with the basics by dissolving the ideas behind 'codswallop' and 'preposterous' into their meaning. Why would you say that they are as you described?

4. ### Ken G

3,615
I am neither a proponent nor a critic of "many worlds", I think all interpretations of QM are simply pictures to have in your mind as you do the calculations implied by the theory. Isn't that what an "interpretation" always is? From whence comes the erroneous idea that an interpretation of a theory is ever a claim on how reality actually operates? If the history of physics tells us anything, it is that physics never gives us that.

5. ### Hurkyl

15,987
Staff Emeritus
The main thing about MWI is that ideas need to be translated. Nearly everything I've heard someone say is "preposterous" about MWI is the result of a failure to translate: someone takes a statement meant to be interpreted by one interpretation, and instead interprets it by a different one.

6. ### ThomasT

This seems to me to be a decidedly sensible and reasonable approach/assessment. I also don't think that doing calculations using standard QM necessarily entails having any pictures about the way the deep reality is.

MWI is one approach to interpreting the deep meaning of QM. Not a very good one, imho.

For the OP, there have been lots of threads at PF on this. And some fairly recent ones that might be informative for you. A most recent one involving, primarily, the views of Hurkyl and Ken G. Check the archives. Read ... read ... read ...

"Codswallop"....nonsense...of little or no use or importance.

Physics is informed by observations and must conform to observations.If a theory or interpretation is to be of any use it must be possible,even if only in principle,to make the relevant observations.How can we make the observations on interpretations such as many worlds?

8. ### Actuality

8
I probably should not have used "preposterous" to describe my disdain for MWI; I agree that it is not technical, nor helpful.

Hugh Everett was clearly an extremely gifted mathematician; however, I believe that he was probably slightly arrogant, and somewhat delusional, to assume that he could explain the entirety of quantum theory in his PhD thesis. MWI is just a fancy mathematical philosophy that can never be tested and is, therefore, worthless in my opinion. The assertion that Daffy Duck collapsed the wave function is just as valid as MWI, in my opinion (LOL).

At least with the Copenhagen Interpretation (CI), it is sensible and useful. I have a lot of respect for Bohr and Heisenberg because they had "quantum humility." It is likely that they understood that the mind of the human species is not capable of understanding the "big picture" of quantum mechanics.

Off Topic: I also strongly dislike quantum mysticism; it irritates me greatly. Particularly the "quantum consciousness" variety.

Last edited: Mar 26, 2012
9. ### Hurkyl

15,987
Staff Emeritus
You know, this sounds an awful lot like "I can't understand something, therefore nobody else can either."

10. ### JamesOrland

93
While that is somewhat true right now, looking at the practical "shut up and calculate" side of it, I do think that eventually we will find evidence for one interpretation or the other. On the other hand, I'm pretty sure the whole point of physics is explaining about the operation of reality, and what is our search for the sadly named TOE if not the search for something to describe how reality works at its most fundamental level?

Now this is probably just a personal opinion, but I think that physics should try to explain reality's actual field of operation. The fact that the outside view differs strongly from the inside view (and thus may be called weird by our merely human intuitions) doesn't make it any less right or describable by physics.

Furthermore, I do think Hawking supports the theory that wormholes could connect two different Everett-branches, but that is... well, very weird to me, and sounds a little bit codswallop-y. Unless, of course, he can find a way to prove it (even if in principle - I haven't the faintest clue how he got to that idea).

Now that is definitely true. I do seem to read a lot of people talking about for instance "splitting of worlds" like some collapse-type process, which is not even a part of the theory.

I know the meaning of the word 'codswallop,' what I meant was that it wasn't a helpful word in describing what your thoughts were on the interpretation.

Also, I'm not a physicist (yet), nor do I know a lot of the meat behind the theory, but I have read about ideas to try to test the validity of Many-Worlds. As I mentioned above, I believe Hawking was thinking something along those lines (but he does seem to have a soft spot for wormholes, doesn't he?), and also Tegmark claims that there is evidence for Many-Worlds, somewhere.

Two points, though: one, Many-Worlds (or, as its original name says, relative state) does seem to fall right out of the full and simple application of the Schrödinger Equation. It is a very simple idea, formally speaking, in that you don't need collapse as an actual fact about nature (mind projection fallacy, anyone?), but merely its appearance as a consequence of decoherence. Of course in your calculations you have to suppose something that's like collapse happened, because that's the inside view of the world, but it doesn't affect at all the outside view.
The second point is actually a double point. The first part is that I do think every detail of a theory (up to and including its interpretation) has to be provable and falsifiable, somehow, for it to be valid. About that we agree. On the other hand, that principle should not be applied exclusively to Many-Worlds, but to Copenhagen, too. As I described above, the relative state interpretation merely makes the assumption that everything is described by a wavefunction, including the measuring apparatus (seems pretty trivial to me, the distinction between system and apparatus is a human one not a physical one), and that it evolves according to the Schrödinger Equation at all times. The Copenhagen one seems to introduce an ad hoc tool to describe our the experimental results called 'wavefunction collapse,' but doesn't seem to try to make any sense of it. In my humble opinion, I believe that what I need is evidence in favour of collapse to be swayed away from relative state, and not any evidence to do the opposite.

There is an article by Tegmark that discusses the misconceptions about the Relative State interpretation, about what it says and does not say. It's a very interesting read.

I think that you are a victim of the MWI misconceptions I mentioned above. You should read Tegmark's paper on it. Also, I do not think he was trying at any point to describe the entirety of quantum theory; he was merely irked by the seemingly random collapse postulate (that does not exist in his Relative State interpretation, as neither does any 'world splitting' postulate, it's all decoherence).

I also claimed above that every detail of a theory should be able to be tested, and the fact that we haven't been able to test it yet does not mean it is untestable.

Furthermore, I also disagree with you that we are incapable of understanding anything. (It's only in trying the impossible that one can truly grow as a human being...) It is very much true that our savannah-optimised brain isn't the best tool to analyse such deep details about reality, but I think you're underestimating the human brain's power and ability to grow.

I agree with your first sentence, but I have no idea what "quantum consciousness" is or would be. Where did you hear that?

11. ### Actuality

8
You might be correct; maybe I do impose my beliefs on other people to a certain extent. However, I would disagree with you regarding terminology. I would replace the word "understand" with the following: "come to any firm conclusions on." Even if you're a proponent of MWI, it is simply an untestable belief and hypothesis, in which case you cannot come to any firm conclusions either.

The human being is, for the most part, an exceptionally intelligent mammal. However, I agree with Lawrence Krauss' assertion that we need to have "cosmic humility." Although we like to think of ourselves as omniscient, our brains have only a finite capacity. Take the size of the human brain in comparison with earth (an infinitesimally small speck in the universe), let alone the cosmos. We're tiny organisms with egos larger than the universe itself. I believe even a mathematical genius with an IQ of 230 who develops a "Theory of Eveything" would be able to perceive the universe only in a limited manner (inside the limits of mathematics, logic and reason). We should continue to utilise quantum theory to our scientific and technological advantage, but it is a pointless endeavour to try and fully understand it.

In conclusion, the entire universe is far (FAR) more complex than anybody is capable of ever fully understanding, this is obviously arguable, but it is my opinion nevertheless.

Last edited: Mar 26, 2012
12. ### Actuality

8
All of the "quantum garbage" that Stuart Hameroff rants about; he believes that human consciousness is a fundamental property of the universe, and endeavours to appear intelligent by using quantum mechanics to explain the origin of consciousness. Again, another pretty and non-falsifiable, egotistical philosophy. He appears on the annoying quantum mystical documentaries, such as "What the Bleep Do We Know!?".

13. ### JamesOrland

93
Untested, not untestable. One is reminded of Lord Kelvin's statement that the movement of muscles was infinitely beyond science. The fact that no tests have been able to discern between Copenhagen and Many-Worlds doesn't mean none will ever be developed - and because of that, Copenhagen and Many-Worlds are equally valid because what we observe is predicted by both theories, so currently favouring one theory over the other is a matter of mathematical taste. And it does look more tasteful (one could say elegant) to throw away unnecessary ad hoc postulates such as the wavefunction collapse. Which is what I mean when I say that I would need evidence to sway me towards Copenhagen.

I again disagree. I also adhere to Tegmark's idea of a purely mathematical universe, so mathematics, logic and reason are nothing less than what you need to understand the universe. And while it may be that our egos are rather inflated, there is no evidence whatsoever so far that what we currently know is the limit of what is knowable to a human being, since almost everything that has been found so far was eventually met with a physical/mathematical theory that explains it, sometimes elaborates on it, and even makes novel predictions, and all those theories were created by human beings.

More than that, to think that the limit on a human brain is something that cannot be changed also seems to me rather silly. Our IQs on average grow as time passes, and what was once considered an IQ of 170 nowadays might be called a 110. What I mean is that we as a species grow more intelligent as time passes, and I, as a transhumanist, think that if we ever do reach a biological limit to our processing power, we will be able to break even that limit with the technology we create.

It is just not correct to think that anything that has been thought so far is the limit of what is thinkable. I myself have never studied deeply the mathematics behind Q.M., my knowledge there is sorely missing (the closest I came to that was one-dimensional Schrödinger Equation), but the theory to me seems, however counterintuitive, understandable.

AH. That. I do think it is falsifiable, though, once we develop AI. If consciousness is ontologically basic, one should never be able to create it from other, smaller parts, right? Like electrons, we can't make electrons out of other stuff. So if we manage to make consciousness out of electrons and all that, I do think his theory falls apart.

And this may be out of place in a forum such as this, but I detest that movie.

14. ### Actuality

8
James,

Thank you for your articulate and interesting response.

Fundamentally, what we're disagreeing about here is purely subjective philosophy; there are obviously no firm absolutes. As I am a scientist by nature, I do not dogmatically hold a belief if the evidence points to another direction; I always follow the evidence. However, science, mathematics and pure logic have limits.

For me, there is a point in reality where mathematics and pure logic appear to be inadequate tools in terms of providing a ground of explanation for certain concepts. For instance, subjective consciousness, love and luck are very difficult to explain from a reductionist perspective. Yes, with love we can analyse the neural correlates of the monoamine system in the brain and develop mathematical models, but can the subjective experience of love ever be explained by mathematics? I very much doubt it! Artificial Intelligence is not even remotely close to human-esque consciousness, and I doubt that it ever will be.

To reiterate, philosophy is always arguable; however, it is a personal belief that mathematics and logic are too limited in scope to explain the entirety of the universe. I have come to accept that certain things are simply inexplicable.

15. ### JamesOrland

93
Hmm, yes, indeed, that is where we differ.

I believe everything, including subjective consciousness, love and luck, is explainable by mathematics, and is in fact a direct cause of mathematics (Tegmark's Ultimate Ensemble theory), and in fact, Tegmark does mention the mathematical model of subjective experiences in his exposition about SAS (Self-Aware Subsystems). That is, I think everything that exists is, in principle, explicable, and I don't see any evidence on the contrary.

And I also think eventually we will be able to build Artificial Intelligence that mimics human intelligence perfectly (and perhaps even surpasses it, with its potential ability of being a perfect Bayesian), and probably will use that knowledge to advance humanity itself beyond the boundaries of mortality. Yes, it does sound like the plot of a sci-fi story, but one can dream (and work to make that dream come true, too).

16. ### Actuality

8
Tegmark's mathematical universe hypothesis is an elegant theory; I am fond of it. I would say, though, that this is ultimately a "faith" position. I would actually prefer it if I could believe that mathematics explains everything, but I cannot force myself to believe something that I do not. If you haven't already done so, I suggest that you read about the limitations of mathematics, so that you can view both sides of the argument.

17. ### JamesOrland

93
Tegmark himself claimed that even his MUH (the Level IV Multiverse) was provable and falsifiable, but I am a bit sceptical about that, at least in the foreseeable future. Then again, I am sceptical about scepticism itself, so :P

Nice, confirmation bias avoidance :)
But I would ask you to recommend me books and/or articles on that subject, because the closest I've ever seen to a true limitation of math was Gödel's theorem.

18. ### Mark M

526
Hi Actuality,

Remember, MWI is by far the most conservative approach to QM (obviously, disregarding Einstein's interpretation, which we know is wrong), it simply states that because the Schrodinger equation does not make wavefunction collapse necessary, it can be dealt away with. The "many worlds" part comes a side effect.

It appears more and more likely that decoherance is a better explanation than wave function collapse. As Everett explained, wavefunction collapse is unnecessary, so, following Occam's Razor, it is best to deal away with it.

To use the example from Everett's dissertation: Imagine two observers A, and B. A is locked within a laboratory, with a particular quantum system S, described by $\psi$. B is outside the laboratory, and can describe the totality of A and S with $\psi ^{A+S}$. Now B would say that $\psi ^{A+S}$ was evolving according to the Schrodinger equation as per usual. But what if A takes a measurement on S? What happens according to B?

The idea of parallel universes comes from Everett's assertion that you can describe the universe as a quantum state. So, as this wavefunction evolves, we get the "splitting" of universes. (to use a terrible term)

Though, I have to say this: the debate is really irrelevant, because as Ken G said, all that matters is the fact that we can use the equations of quantum mechanics to describe particles. No matter what the interpretations, the equations do not change, so even if somehow an interpretation was confirmed, quantum mechanics would not change. On top of that, almost no one says any interpretation can be confirmed, making it more of a philosophical question in some cases.

19. ### Hurkyl

15,987
Staff Emeritus
Don't discount pedagogy. The way a subject is presented can make it easier or harder to learn. The way knowledge is organized can emphasize and clarify certain aspects while at the same time being misleading or otherwise obscuring other aspects.

As an aside, from what I've learned about the history of QM (and long before I had learned about other interpretations like MWI or deBB), I have the impression that the only reason collapse-based interpretations were ever embraced was simply because people thought it was the only choice.

And, apparently, some people still think that way, because my early readings had informed me of a impossibility proof of alternative interpretations, which I now know to be flawed. (which roughly boils down to "collapse is not unitary, so you can't reproduce it by unitary evolution")

20. ### Actuality

8
Hi Mark,

I do not have a problem with the concept of decoherence. There are a multitude of ways in which one can interpret the collapse of the wave function or, indeed, the "appearance" of collapse. It's all a matter of subjective interpretation of the evidence. Is there any evidence that the collapse of the wave function is an epiphenomenon? If so, could you point me to this?

There is one main reason why I specifically dislike MWI and is as follows: it grafts on a set of extremely counter intuitive ideas, way beyond what is actually testable. I, for one, believe many of its components are unfalsifiable. Granted, "counter intuitive" does not automatically equate to erroneousness, but still.