The measurement problem, Copenhagen, pilot-wave, and many worlds

With quantum physics, we have a situation where a quantum object, such as a photon, electron, atom or similar scale entity, acts like a wave, spreading out in a superposition, until we look at it (by measuring it in some manner), then it behaves like a particle.  This is known as the measurement problem.

Now, some people try to get epistemic about this. Maybe the wave isn’t real but just epistemic probabilities. The issue, shown in the double-slit experiment, is that the wave interferes with itself, something those who want to relegate the wave to completely non-real status have to contend with.

An important point is that if the wave is very spread out, say light years, and any part of it is measured, the whole thing collapses to a particle, apparently faster than light.  This appears to violate relativity (and hence causality), which was Albert Einstein’s chief beef with quantum physics, and the impetus behind the concept of entanglement explored in the EPR paradox.

Now, we have an equation, the Schrodinger equation, that models the evolution of the wave.  Its accuracy has been established in innumerable experiments.  But when we actually look at the wave, that is, attempt to take a measurement, we find a particle, that subsequently behaves like a particle.  The math appears to stop working, except as a probabilistic prediction of where we’ll find the particle.  This is often called the wave function collapse.

The Copenhagen interpretation handles this by saying that quantum physics only applies to small isolated systems.  As soon as something macroscopic is involved, such as a measuring device, the rules change.  Kept to a minimal instrumental version, I think this interpretation is underrated.  Bare bones Copenhagen doesn’t attempt to explain reality, only describe our interactions with it.  It could be seen as an admission that the metaphors of our normal scale existence are simply inadequate for the quantum realm.

Of course, people can’t resist going further.  Copenhagen is actually more a family of interpretations, some of which involve speculation about consciousness causing the collapse.  Reality doesn’t congeal until we actually look at it.  I think the challenges of quantum computing rule this out, where engineers have to go to extreme efforts to preserve the wave to get the benefits of that type of computation.  They’d probably be very happy if all they had to do was prevent any conscious mind from knowing the state of the system.  But it’s an idea many people delight in, so it persists.

The pilot-wave interpretation, often referred to as De Broglie-Bohm theory, posits that there is both a particle and a wave the entire time.  The wave guides the particle.  When we look / measure, the wave becomes entangled with the environment, it loses its coherence, and so the particle is now free to behave like a particle.  This idea actually predates Copenhagen, although it wasn’t refined until the 1950s.

Pilot-wave initially looks promising.  We preserve determinism.  But we don’t preserve locality.  Looking at the wave, anywhere in its extent, still affects the trajectory of the particle, even if the particle is light years away.  So, Einstein wasn’t happy with this solution, since relativity appears to still be threatened.

Hugh Everett III looked at the above situation and asked, what if the math doesn’t in fact stop working when we look?  Our observations seem to indicate that it does.  But that’s failing to account for the fact that macroscopic systems, including us, are collections of quantum objects.

As it turns out, the Schrodinger equation does predict what will happen.  The wave will become entangled in the waves of the quantum objects comprising the measuring device.  It will become entangled with the environment, just as pilot-wave predicted, but unlike pilot-wave, Everett dispenses with the particle.

Crucially, rather than collapsing, the superposition of the wave will spread, just as it seems to do before we look.  Why does it appear to collapse?  Because it has spread to us.  We have gone into superposition.  Every branch of that superposition will now continue to spread out into the universe.  But the branches are all decohered from each other, each no longer able to interfere with the other.  They are essentially causally isolated.

So each of those branches could be romantically described as being in its own separate “world”, resulting in many worlds, the many worlds interpretation.

The appearance of the collapse, under the many worlds interpretation, is because we are now on one branch of the wave function, observing the small fragment of the original wave that became entangled with this branch of the environment.  Under this interpretation, there is a different version of us in each other branch seeing differing parts of the wave, which we now refer to as a “particle”.

Which of these interpretations is true?  Copenhagen, pilot-wave, many worlds, or some other interpretation?  They all make the same observable predictions.  (The ones that don’t were discarded long ago.)  It’s the predictions they make beyond our ability to observe that distinguish them from each other.

We could ask which has the fewest number of assumptions.  Most people (often grudgingly) will admit that many worlds has the most elegant math.  (Evoking comparisons with Copernicus’ heliocentric model in relation to Ptolemy’s ancient geocentric one.)  And it does preserve realism, locality and determinism, just not one unique reality.  Whether that mounts to fewer assumptions than the others is a matter of intense debate.

Each interpretation has a cost, often downplayed by the proponents of that interpretation, but they’re always there.  Quantum physics forces us to give up something: realism, locality, determinism, one unique reality, or some other cherished notion.  As things stand right now, you can choose the interpretation that least threatens your intuitions, but you can’t pretend there isn’t a cost.

Unless of course I’m missing something.

66 thoughts on “The measurement problem, Copenhagen, pilot-wave, and many worlds

  1. Hey, looks like someone was inspired to try his own posting marathon. 🙂

    “We could ask which has the fewest number of assumptions.”

    That’s an oft fired arrows from the quiver. Given the issues MWI raises (which its proponents don’t seem able to respond to), this isn’t a strong argument.

    It seems arguably a false argument to me. It may remove the assumption of collapse, but adds the assumption of creating entirely new universes out of nothing. And that math is real. Those are big assumptions. I thought creating universes required a Big Bang. And I didn’t think math was real.

    Which is the main argument: “Hey, just following the math, boss!” The last time we talked about this you didn’t think MWI was fundamentally Tegmarkian, but I don’t see how it isn’t if the central argument involves the reality of the Schrödinger equation. If it isn’t math, what is it? What do you think the wave function is?

    If that all works for some, fine, but, as I said in another thread, it’s increasingly inexplicable to me that anyone thinks this is anything other than a mathematical fantasy akin to String theory or SUSY or the BUH. They’re all cases of getting lost in math.

    Liked by 1 person

    1. I actually didn’t plan to do a post a day. Circumstances just worked out that way. This one started as a reply to Eric’s question in another thread about quantum physics, but it grew until I pasted it in the post editor.

      So, are time dilation, length contraction, and mass increase, assumptions of special relativity? Or are they consequences of accepting that the speed of light is constant in all frames of reference? Was the big bang, as worked out by Georges Lemaitre in the 1920s, before Hubble’s observations or discovery of the CMB, an assumption? Or an extrapolated consequence of general relativity?

      I don’t think we can count a theory’s consequences against it when judging its parsimony. MWI actually removes an assumption, and still explains our observations. It may still end up being false. Its consequences are so bizarre that we’re right to be cautious in accepting it as more than a candidate for reality until someone figures out a way to test it.

      But given that reality has repeatedly shown itself to be absurd, I find summary rejection of it unjustified.

      Liked by 1 person

      1. I know what you mean. I’ve had comments expand into posts, too. We’re just… detailed. Yeah, that’s it, detailed. 😉

        If you’re going to cite the few cases in science where someone turned out to be right, you really should also cite the many more times scientists turned out to be wrong. Of course we remember the winners. (It’s an argument that can work against MWI — most extreme theories turn out wrong.)

        “I don’t think we can count a theory’s consequences against it when judging its parsimony.”

        Even when the consequence is a distinct lack of parsimony? When the consequence is an explosion of realities?

        “MWI actually removes an assumption…”

        If it works for you, it works for you. I’m made skeptical by ideas that come with slogans.

        “I find summary rejection of it unjustified.”

        Give me some credit; my opinion is “considered,” not “summary.” Carefully and at length, in fact. I’ve been chewing at this for years.


        1. I’m actually trying to reduce the length of my posts, but it’s turning out to be harder than I expected.

          The cases I cited weren’t about them being right, but about the distinction between assumptions and consequences.

          On an explosion of realities, one of the reasons 16th century astronomers rejected the Copernican model is because the stars didn’t show detectable parallax. Everyone realized the answer could be that they were just too far away, incomprehensibly far away. It seemed like an utterly ridiculous idea at the time. But that was a consequence of the Copernican model, not an assumption. Our understanding of reality has expanded many times over the centuries. I can’t see it as a logical reason to reject a theory.

          On “chewing at this for years”, I’m confused. Just recently you said that you’d never had much interest in the MWI, which at the time fit with your lack of familiarity with the role of decoherence.


          1. “I can’t see it as a logical reason to reject a theory.”

            All I can say is that I draw a distinction between the physical realities you listed and the mathematical explosion of infinite realities posited by Everett.

            It is, in any event, something of a strawdog, because my actual argument, which you don’t seem to want to engage, involves energy and probability.

            “Just recently you said that you’d never had much interest in the MWI,”

            Okay,… that was a comment I made on March 14 in reply to Michael, who said to me, “I’m curious how the idea has evolved over the years, and whether or not Everett’s original use is consistent with the ideas today or not. Do you know?”

            Which, no, I don’t know the history of because I never had that much interest in MWI (because I’d looked into it a few times and didn’t buy it as a real explanation). You may recall my story about a guy I met in the 1990s who prefaced his explanation of belief in MWI by saying I’d think he was crazy little knowing I was quite familiar with the theory at that time.

            You should also cite my March 1 comment on that same post that starts, “I have long thought explaining decoherence is key to understanding the quantum world. One theory I’ve heard suggests it’s due to gravity, so decoherence happens when an interaction involves something with enough mass to have enough gravity. It would explain why coherence is a small-scale thing.”

            Dude. I’ve been into quantum mechanics since before quarks.


          2. I’ve noted several times that the energy issue concerns me as well, although there are answers for it.

            Carroll himself admits that probabilities are an issue that needs to be worked out. Personally, I still don’t see what the big deal is. They just go from being ontological to epistemic. But enough physicists are concerned about it that I keep trying to understand the issue.

            On that same thread, you also stated that you thought the MWI assumed no decoherence, conflating it, I think, with the wave function collapse.
            All I’m saying is you may not understand this interpretation as well as you think you do.


          3. Having taken time to go over that thread, watch that video again, and go over Everett’s paper, I stand by what I said, although I could have said it more clearly. (FWIW, neither the word parts “coh” nor “decoh” appear anywhere in Everett’s paper. The closest is a “deco(mpos)” part seven times.)

            In the video, O’Dowd argues that decoherence explains why we can’t see other branches. It’s also used to explain wave-function collapse. Either way it seeks to explain the appearance of collapse, either due to branching or due to the decoherence itself.

            As such, as I said, it has nothing to do with MWI in terms of explaining the splitting and existence of multiple real worlds. (Just why we don’t see them.) Further, because Everett doesn’t accept collapse, there is no decoherence in any individual branch. The coherent phase of the particle merges with the coherent phases of the measuring device (as illustrated in the video), those coherent phases interact with larger systems and so on.

            Under MWI, systems maintain their coherence. That’s his point: the wave-function abides.


          4. Yes, it reads: “In many-worlds, the subjective appearance of wavefunction collapse is explained by the mechanism of quantum decoherence.” (emphasis mine)


          5. Per your own Wiki quote, decoherence dates back to Bohm in 1952, so the idea existed in 1957 for Everett.

            This is easily settled. Go through Everett’s paper and see if there is any language that even resembles the idea of decoherence. (There definitely isn’t any that uses “coh” or “decoh” word parts.) I went through it again last night, and couldn’t find anything. Maybe someone else can.

            From what I can determine, Everett depends on statistics to account for subjective experience (which he does speak of in explaining why an observer with superposed states sees only one outcome). But he is quite clear that the “measured” system combines with the “measuring” system without any loss of wave-function information.

            Here’s a bit of his math:


            It says roughly that the wave-function for a System+Observer is a summation of states of an observable quantity, a_i, the wave-function of the System, \phi_i, and the wave-function of the Observer, \psi^O_i. The subscript, i, denotes the superposed states of possible observations. The square brackets denote the Observer’s memory; the dots representing the memory state up to the observation, a_i, which alters the Observer’s memory.

            Everett then explains using statistics and measures over configuration spaces to explain why a_i is seen by the Observer as a definite state rather than a superposition.

            (Caveat: AIUI. I’m obviously going to have to learn to do wave-function math to get deeper into this.)

            But I can find no sign of decoherence. That’s something that’s been added later (as you said) to try to justify our subjective experience. But as O’Dowd said in the video, it’s an argument, not a given. It’s what some analysts think about MWI.


          6. Wyrd,
            I’d suggest you do some reading on decoherence. No information is actually lost in it. It’s just dispersed into the environment. Decoherence is entanglement with the environment. It’s widely recognized to be similar to, if not the same mechanisms Everett and Bohm were describing.

            This is pretty basic stuff that can be understood from reading any careful account of MWI. (Unfortunately, polemical accounts rarely include these details.)


          7. Again: Show me where Everett invokes it or anything like it.

            Again: That’s something that’s been added later (as you said) to try to justify our subjective experience. But as O’Dowd said in the video, it’s an argument, not a given. It’s what some analysts think about MWI.


          8. Sorry Wyrd. I’m not parsing Everett’s 100+ page paper just to prove basic facts you can get from several contemporary sources.

            Even if you read those sources, decide the PHDs are all wrong, and that decoherence was added later, it doesn’t matter. It’s arguably the modern theory and its integration into current understanding that you should be engaging with.


          9. Mike, for such complex topics as you handle, making your posts shorter may be hard. But if you could manage it, lazy people like yours truly would be really happy

            Liked by 1 person

          10. Thanks Mak. I’m hoping to get the average size down. It probably means I need to make the topics more focused and be more ruthless in editing out irrelevance. Hard for a big mouth like me. 🙂


  2. “It could be seen as an admission that the metaphors of our normal scale existence are simply inadequate for the quantum realm.”

    I isolated this particular statement because it essentially says it all Mike. Metaphors and analogies are valid for the “thing”, which are the metaphors and analogies themselves; but they are not valid and absolutely useless for the “thing-in-itself”, which is the true nature of reality.

    Trying to explain an unknown, let alone give meaning to it using a metaphor or an analogy of any kind is akin to setting oneself up to drink the Kool-Aid prepared by a very talented, persuasive priest. I can’t help but agree with Eric that our beloved institutions of science have morphed into the business of entertainment. Its the same thing Sabine Hossenfelder continuously harps about. There haven’t been any new discoveries for decades using the same old worn out a posteriori methods. Reductionism has reached its lower limits. Hell, the only thing that is left is to take the show on the road as a Vaudeville act. Either that, or get down and dirty with some hard-core metaphysics. Metaphysics, there’s that dirty little word again.

    Dudes, none of my metaphysics rely upon, nor do they use analogies or metaphors. I would think that would a least be note worthy???????


    Liked by 1 person

    1. Lee,
      I fear that when talking about or contemplating reality outside of our immediate sensory environment, metaphors are unavoidable. Usually when someone tells me they aren’t using them, then gives their spiel, I find metaphors in it. Which isn’t a failing. It’s the only way a primate from the African savanna has any hope of navigating and manipulating the wider world and universe.


      1. Mike,
        When I state that the properties that make up a system are the experience of the system, regardless of whether that system is an elementary particle or mind, do you consider that a metaphor or just plain hand-waving? Personally, I consider it ground-breaking metaphysics.

        Let’s talk specifics here: According to the standard model of physics, mass, spin and charge are the properties of elementary particles therefore, according to my metaphysics, mass, spin and charge are the experience of elementary particles. Elementary particles are what constitute atoms. There are approximately one (1) followed by twenty-seven (27) zeros atoms that constitute my properties as a system.

        Now let’s talk about one of my personal experiences called vertigo ( for the record, vertigo could be considered quailia by those who prefer coy terms). Do you believe that when I close my eyes and everything starts spinning in my mind, that this experience of spinning is not a property of elementary particles, the very elementary particles that constitute the 1,000,000,000,000,000,000,000,000,000 atoms which constitute me as a system? Would it even be possible for the system of mind to experience spin if spin was not a fundamental, elementary property of all systems?

        Just thinking out loud here: The shit that goes on in this place has a simple explanation. It isn’t magic folks.



        1. Lee,
          I think the concept of an elementary particle is a metaphor. Mass, spin, and charge are more difficult, since to a physicist these are largely mathematical concepts. But when we otherwise discuss them, I think we’re doing so in terms of metaphor.

          The statement that mass, spin, and charge are experience is, to me, an ambiguous one. It hinges on what you mean by “experience.” If you mean that word in the way it’s normally used, then I think that usage toward particles is metaphorical. I know a panpsychist may disagree. 🙂

          Those properties in our atoms may be part of the ultimate infrastructure that supports our experience, but the same properties are also in the ultimate infrastructure of WordPress or Minecraft. Of course, a panpsychist might say WordPress and Minecraft have experience, so I guess it’s a consistent loop.


          1. You’re straw manning now Mike. Technically, even your own image in a mirror is a metaphor, As far as the meaning of “experience”, I didn’t realize the term “experience” was such a tricky word.

            Your last comment sums it up best though: “… a consistent loop.” Logical consistency, one that contains zero contradictions, exceptions or paradoxes is the key to a successful theory.



          2. According to my metaphysics Mike, consciousness is universal therefore, consciousness becomes fundamental in explaining not only the diversity and novelty of the expression, but also the why and how that novelty and diversity occurs.

            Utilizing a concise and pragmatic definition of consciousness, one that is all inclusive; the term consciousness can be substituted to replace the archaic, heartless word “evolution”. The term evolution is grossly ambiguous, misleading and is a mystical, magical word that everyone throws around with reckless abandonment in an attempt to explain the how and the why of the novelty and diversity of our universe without invoking some form of teleology. Evolution is a word that has outlived its usefulness, time to eschew it and replace it with the word consciousness.

            Here’s a prediction that can be empirically verified with 100 percent accuracy: Since consciousness is universal therefore, all discrete systems will possess a limited degree of self-determination in an otherwise deterministic system. It is this limited degree of self-determination that explains the otherwise inexplicable behaviors of physical systems like mind and human behavior, including but not limited to the system of rotational patterns of planets within our own solar system. As elegant as the math is behind GR, general relativity cannot, and will never be able to predict the rotation of planets in our solar system with 100 percent accuracy. No mathematical model will. You can take that prediction to the bank…



          3. Interesting. I actually see “consciousness” as the hopelessly ambiguous word, malleable to such an extent that, used in an unqualified manner, it has no scientific meaning. Most of the arguments about it seem like definition disputes in disguise. The point of that hierarchy I keep bringing up is to highlight just how protean the term is, and what is typically missing when it’s applied to simple systems.

            Not that the term “evolution” is immune to those issues. Any commonly used word is going to develop variants. But within biology, its definition is fairly precise, even if there is often controversy about the mechanisms.

            But the hopelessly ambiguous way “consciousness” is used means it lies in the eye of the beholder. I can’t tell you that you’re wrong that all those systems are conscious. I can only point out what capabilities they’re missing.


          4. Thinking of every thing as a physical “system” is the right place to start. Now, the ability to liberate the word consciousness from its exclusive correlation to mind and all of the entrenched baggage that comes with that correlation will an impossible task. The mind/matter dichotomy is thousands of years old, and the same age old arguments are still a part of our modern culture. I keep harping about it Mike, but subject/object metaphysics is the intellectual prism through which human beings view the world, and SOM is responsible for creating problems that fundamentally do not exist. It really is that simple…



          5. I think the issue for me Lee, is that saying consciousness is everywhere, shifts the focus of concern from what makes something conscious, to what distinguishes animal consciousness from plant, unicellular, storm, rock, or proton consciousness. It seems to just change the terminology while leaving the same actual problems.

            As I’ve noted before, I do agree with the perspective that there’s no magic moment where before there wasn’t consciousness, then there is. But for me, this is a gradual emergence, rather than some fundamental essence that’s everywhere.


          6. “I think the issue for me Lee, is that saying consciousness is everywhere, shifts the focus of concern from what makes something conscious, to what distinguishes animal consciousness from plant, unicellular, storm, rock, or proton consciousness. It seems to just change the terminology while leaving the same actual problems.”

            I can see that being an issue if one is only interested in the field of neuroscience and wonders how the phenomena of mind emerges from the gray matter in our skull. Plus, for whatever reason, you choose to believe that the notion of consciousness is exclusively limited to the phenomena of mind. It’s a Cartesian sort of thing I guess…

            Anyway, I’m not too disconcerted with your personal position. I can appreciate that different folks have different interests. Hell, I’ve got an acquaintance of mine who believes with all of the fiber of his being that the earth is flat. It’s the only thing he’s interested in, and the only thing he wants to talk about……. it’s all cool.


            Liked by 1 person

  3. That is a really good explanation of MWI and pilot-wave theories. I’d like to think I helped a little on the MWI part 🙂

    My favorite QM interpretation is actually John Cramer’s Transactional interpretation. Favorite as in, that would be really cool, not necessarily as in, is most likely correct. The idea is that “advanced” waves (“traveling” backward in time relative to our usual sense) and “retarded” waves (the ones physics texts usually focus on) have a “handshake” which settles what happens.

    Liked by 1 person

    1. Thanks Paul. You’ve definitely given me things to chew on, and sent sources that helped.

      The Transactional interpretation sounds wild. Waves intersecting each other in time. That interpretation wears its costs on its sleeve.


      1. That’s what I thought at first, but now I’m not so sure. Specifically, I thought it required more assumptions about boundary conditions: a set of them in the future, and another in the past. But looked at differently, it’s just a lot of events behaving in consistent patterns – which also goes for Everett or Bohm. I’m not sure it requires significantly more complexity (as in Kolmogorov complexity) to encapsulate.


  4. [rummaging through pockets. … looking for … ah, there … two cents]

    Part of the problem I see, and I think is mentioned above, is that people have intuitions based on being medium sized things dealing with the medium-sized world. So when we try to think about things that are really small, we think in terms of the really small things we know about, like particles. We can’t get over the fact that things like electrons are not particles.

    So for example, someone might mention how surprising it is that some hunk of metal is really mostly empty space. It’s not mostly empty space! All that space is filled up with electrons and protons and neutrons. Electrons are not particles. When we say an electron is in a specific orbital, it’s not some tiny thing moving around the orbital, it’s a thing the shape of the orbital.

    When an electron goes through the two slits, maybe it doesn’t go through one or the other. Maybe it just fails to interact with the barrier. Maybe the two-slit barrier simply filters out certain electrons. Maybe those electrons which get through do so because they have a feature which is best expressed in math that looks wave-like. Maybe when it does interact at the detector, it interacts with exactly one other thing in one place, as opposed to a wave which interacts at multiple places. This doesn’t mean it collapses into a particle when it interacts. It just means it interacts with one thing at a time.

    To visualize something like this, I consider a yard stick. Suppose you are in a dark room on the space station (so, no gravity) and there are yardsticks floating in this room (and nothing else), but you can’t see them. The only thing you can do is to throw other yardsticks into the room and listen. You have acoustic equipment and computers to pinpoint any sound. So when two yardsticks collide, they interact at a point. But we don’t say the yardstick collapses to a particle at that point. That’s just how it interacts.


    Liked by 2 people

  5. [Oh look! Two more cents … ]

    The other options for explanations not mentioned above are the epistemic options. These options say that the Schrodinger equation doesn’t describe what reality is, just what we can know about how things interact. These options can have the simplicity of the many worlds interpretation without, well, the many worlds.


    Liked by 2 people

    1. Your two cents are always welcome! (And additional ones as well!)

      As I noted in the post, I definitely think we can’t exclude the possibility that our minds simply aren’t equipped to model the dynamics at that scale. All the metaphors from the scale we’re most familiar with may simply not work. That said, no one is really satisfied with that answer. We want to understand, if at all possible.

      On your first description, the thing is, the electron interferes with itself, apparently all up and down the wave. It isn’t localized. And if we have two electrons interact, they could become entangled, their waves interacting all up and down the waves. Using your yard stick metaphor, it would be like individual yardsticks interacting all up and down their length, but as soon as we introduce enough of them, we’re no longer dealing with yardsticks, but only a small pieces.

      On epistemic, that’s a variation of what I said above, but I think the interpretations that hide behind that are, well, hiding, not dealing with the issues. We already have a “Shut up and calculate” interpretation. I don’t know that additional ones add much.

      As I noted in the post. There’s always a price to pay. If you think you’ve avoided it, you’ve probably overlooked aspects of the problem. If you were really to find such a solution, there’s a Nobel waiting for you. It’s harder than it looks.

      Liked by 1 person

      1. Regarding “entanglement”, I’m not yet convinced that isn’t also an epistemic issue. As far as I can tell, two systems being entangled simply means they have interacted (or causal ancestors interacted), but you haven’t interacted with any of them (or those ancestors), so you just don’t know how that interaction went.

        I’m not sure where you got the idea of two electrons interacting “all up and down the waves”. Is there a source for that, or are you winging it? 🙂 And for the yard sticks, interactions at a point do have effects all along the length of each. Also, don’t know what you mean by saying as we add lots of yardsticks you end up with small pieces.

        As for the epistemology, I think it gets back to “you can’t know what reality is, only what it does”. Sometimes you find that what it does can be expressed in nice shorthand equations. F=ma. Schrodinger eq., etc. The equations are useful, but they can’t tell you what reality *is*. (Cuz multiple realizability.)



        1. You caught me! I overstated the case with “all up and down the waves.” My bad. The point I was trying to make is that when the particles interact in isolation, they don’t collapse, at least not from the perspective of the outside world. They interact as waves, and their evolution can now be modeled on a common wave function.

          Definitely we can always fall back to an epistemically conservative position and eschew any speculation. To me, that’s the classic version of Copenhagen I noted in the post, the “Let’s take our mathematics and cookbook and be happy” approach. That approach was dogma for several decades. Many of us aren’t satisfied with it, but it’s always possible we’ll have to live with it.

          On your yard stick analogy, I wonder where that line of reasoning might lead. Strings? Just a thought, probably driven by ignorance.


  6. Mike,
    This post seems like a great prequel for my recent question to you about the many worlds interpretation of QM (over here: Now that you’ve provided it however, there’s also my question itself.

    As I understand it, “many worlds” proposes that whatever happens in our universe is caused to, and so is deterministic, though each of the unfulfilled probability potentials occur as well through the spawning of separate universes. These realms are exactly like ours, except for the noted QM difference to each of them. Thus within a cubic millimeter of space in our universe, there should tend to be gazillions of new universes spawned each second given the unfulfilled probability potentials associated with general quantum dynamics within. Or equally funky, it could be that MWIers believe that extra worlds can only emerge once a teleological agent attempts to measure something. Thus instead of “über magic to the nth degree”, I suppose I’d assess their position as something more like “anthropocentric über magic”. Either way I guess that the proposed extra worlds, unless radically different from ours, would also spawn extra worlds by means of their own QM, and so on for infinite regress.

    In any case, am I mistaken about the implications of MWI? Are either of these being proposed, or rather something else?

    Liked by 1 person

    1. Eric,
      As I noted in the other thread, this post started as my reply to you, but it obviously grew. 🙂

      One of the things I tried to make obvious is that the language of new universes can be misleading. If we define a “universe” as a causally isolated system, then yes, under MWI, new universes get created with each quantum interaction. However, this isn’t an instant new spacetime tens of billions of light years wide, but a new branch that gradually expands out from the interaction. If spacetime isn’t quantum, then all the branches may coexist in the same spacetime, similar to the way different radio signals can coexist on different frequencies.

      Remember, these other universes are not an assumption of the interpretation. All MWI does is remove Copenhagen’s assumption of the wave function collapse. The result is our observations are still explained, but with the consequence that all the other probabilities also play out.

      MWI actually has no special role for consciousness. The idea of things only existing once a conscious agent looks at it can be viewed as a variant of Copenhagen, although the Wikipedia article on quantum interpretations breaks it out as its own interpretation, which I think is more accurate. But again, that is not MWI. There is a variant called “many minds”, but I don’t know much about it, and it’s not the classic version of MWI.

      As I noted, you can say that quantum mechanics is deterministic, but having it be so involves costs. If you want the classic macroscopic physics framework: determinism, locality (Einstein’s wish), and continuous realism, then your options are limited.

      Liked by 1 person

      1. Mike,
        Whether or not these proposed isolated systems share our spacetime is not what concerns me. What concerns me is the notion that our desire to come up with a deterministic answer, leads us to theorize that in each cubic millimeter of space, bazillions of nearly identical realms are created per second, and they in turn create their own, and so on for an infinite regress of otherwise isolated worlds. (They’re not entirely isolated, since one would emerge from the other.)

        If we had some generally accepted principles of metaphysics, epistemology, and axiology from which to found the institution of science, then I doubt that people would get sucked into such “brain candy” nearly as strongly as they do today. Sean Carroll is an amazingly skilled priest. I’d like to give his prey some better tools from which to resist such nonsensical speculation.

        I’m not saying that QM is deterministic. I’m saying that if it’s not, then it reflects a reality which functions magically. My single principle of metaphysics suggests that we need two varieties of science — one where scientists presume that causality remains absolute, even when we clearly don’t grasp what’s going on, and another where scientists permit themselves to theorize the existence of supernatural dynamics. Beyond Cartesian dualism, it seems to me that theories of non-mechanism based qualia would find a home in the “causality plus” variety of science, and certainly this “many worlds” speculation.

        Liked by 1 person

        1. Eric,
          Consider this. We have a theory which successfully models the dynamics of a system. Yet at a certain point, when we measure it, those dynamics seem to cease. The leading explanation is that there is an event, a very mysterious event, with all kinds of spooky implications, which can’t be explained.

          Now, someone comes along and asks, what happens if that mysterious event actually doesn’t happen? And discovers that if the dynamics continue, they still explain our observations.

          Forget the untestable consequences for a moment. Would that simplification of the theory leading to the same observations be a good move epistemically? If not, why not?

          Liked by 1 person

          1. Mike,
            We do find that the more precisely we measure things, the more variability that’s displayed to us through quantum funkiness. And indeed, it’s quite an exact sort of funkiness in the sense that Heisenberg’s uncertainty principle effectively describes how exactness in one complementary variable will mandate that we find inherent uncertainty when we try to measure the other as well.

            Some say that this is because there’s an elemental randomness to nature itself in the sense that causality fails to provide an exactness to both of these at the same time. I consider this interpretation to be conceding the existence of magic. And it might be the case, though I’d like us to fully acknowledge the associated implications for holding such a position. To the extent that causality fails in an ontological capacity, nothing exists to understand. Here science becomes obsolete in this manner. Thus theoretically we’re in need of two varieties of scientist — one secured by the metaphysics of causality in an ontological capacity, and another that essentially begins there, though when things get too funky is able to fall back upon “another kind of stuff”. Thus Einstein’s famous line about dice playing gods. As you know, I consider more than just physicists to unwittingly dabble in that brand of metaphysics!

            So now on to “many worlds”. As I understand it, the position here is that everything is causally determined to happen exactly as it does in our “universe” (even though we still can’t measure complementary variables exactly), with the non-fulfilled potentials existing as well in their own thusly created universes. So here bazillions of fully functional universes spawn from ours each second, and from each of those as well, thus permitting adherents say that everything which happens here, or anywhere, is perfectly determined to happen exactly as it does. To me this seems like explaining a minor bit of apparent magic, by means of über magic to the nth degree. So that’s why I don’t consider this to be a good move epistemologically. We can always claim fantastic contingencies beyond observation to address such matters.

            I’ve never claimed to be the sharpest pencil in the pack. This morning I went through Wyrd’s new post on the matter, and it gets into all sorts of particulars which some people will have at their disposal, and I never will. But I know what I know (if you know what I mean). I refuse to permit “brain candy” from disguising the implications of what the many worlds QM interpretation happens to be proposing.

            Liked by 1 person

          2. Eric,
            I still doubt you understand the Everettian interpretation, but your final comments seem to set up a self reinforcing feedback loop that it seems unproductive for me to try to pierce. All I can do is caution that if you know there are areas you don’t understand well, having too much confidence in your conclusions about those areas sets up barriers to learning.

            Liked by 1 person

          3. That’s a fair point Mike. There’s good reason that we don’t trust the opinions of non-experts over experts for all manners of speculation. And regarding physics, I’m no expert! Still I’m also suggesting that the specific issue which is being addressed here concerns something that physicists do not specialize in, and that no associated experts yet exist to guide them. Here I speak of how humanity has not yet developed a community of respected professionals with generally accepted principles of philosophy from which to potentially found the institution of science more effectively.

            For the issue at hand my proposal is: To the extent that causality fails, nothing exists to understand. This should segregate science into a variety where the metaphysics of causality is presumed absolute, as well as a variety where it’s not presumed absolute (or a “plus magic” version). The common QM interpretation where causality simply fails, would thus fall under the magical form of science. Note that this could be the case, though nothing would exist to potentially understand in that regard.

            If physicists today were armed with my single principle of metaphysics, as well as were to decide that causal dynamics may exist by which cajillions of full universes similar to our own could emerge every second per cubic millimeter of space here, and that those universes in turn could do the same for an infinite regress, then I’d be very surprised! But correct me if that’s not what the many worlds QM interpretation states, in which case I’ll refine my assessment.

            Liked by 1 person

          4. Eric,
            It’s kind of interesting. My thinking is that even if causality appears to be absent in particular phenomena, I wouldn’t want to give up on understanding it. If in fact QM is indeterministic and non-local, I still want as much of an accounting of what’s going on as possible. I’m not satisfied to say “magic”, there’s nothing here to understand, and walk away. I think science is much more pragmatic than that, and won’t stop investigating just because a situation doesn’t meet particular axioms.

            But what’s a bit ironic here, is the QM interpretation you most vehemently reject, is exactly the one that gives you what you want: causality. Yes, it has metaphysical baggage, but it’s all unseen and untestable. The core theory preserves determinism, locality, and continuous realism. A lot of physicists accept that core part and do their level best to ignore the rest, treating it like the crazy uncle they can’t get rid of and hide away in the attic, but of course, the crazy uncle is the price of admission.

            Liked by 1 person

          5. Mike,
            In not wanting to give up understanding QM, you’re presuming that something does exist to potentially understand. This is to say that in the end you’re presuming causality. Thus you’re interpreting Heisenberg’s uncertainty principle epistemically rather than ontologically, as I do. Many physicists seem to interpret it ontologically, perhaps not realizing this to be an admission of magic.

            I don’t consider there to be anything ironic about my naturalistic disdain for “many worlds”. Are you telling me that if I understood this interpretation well enough, then I would decide that our QM discrepancies might exist because full universes nearly identical to our own instantly emerge at the quantum scale? If so then okay, but to me that sounds like one hell of an “education”. (And yes I do quote the term for a reason. We can learn to believe in all sorts of miraculous ideas. For me personally, that one would be hard to swallow.)

            It surprises me that people are so concerned about preserving locality and a continuous reality. I personally don’t mind sacrificing them. Locality concerns three spatial dimensions of existence, and continuity concerns one that’s temporal. Thus if there are any dimensions of existence beyond these four, then we should expect circumstances where locality and continuity fail, though in a natural way. Note that here determinism could remain absolute, or the price of admission to the perfectly causal brand of science.

            Liked by 1 person

          6. Eric,
            I don’t think I’d agree that I’m presuming causality, at least not deterministic causality. I’m prepared to accept indeterminancy. Reality may be stochastic at its lowest layers. That would be hard for us to accept. We usually think of randomness being emergent from a clockwork universe, but QM forces us to confront the possibility that it’s the reverse.

            On MWI, no, that’s not what you would decide, although you might understand why some people choose to describe it that way.

            Well, if determinism is your thing, and MWI is verboten, your best bet may be pilot-wave, deBroglie-Bohm theory. It’s deterministic although not local. Apparently it’s not without its own problems, but then they all have issues.

            I actually have a harder time accepting non-locality, for the same reasons Einstein did (although I will if there’s evidence). If events happen at a distance, which plane of simultaneity do they take place on? There are people who say it’s compatible with Einstein’s theories, but only because we can’t make use of it. But I think Einstein was right to dislike that possibility. It would undermine SR and GR as fundamental theories.

            Liked by 1 person

          7. Mike,
            You can go with a stochastic perspective in an ontological capacity on QM if you like, but that would also put you on the supernatural side of things under my single principle of metaphysics. This is to say that if something ever happens which was not caused to happen exactly as it does, then the only way for it to exist as such would be by means of a kind of stuff other than the causal variety. Conversely for the standard kinds of stuff, cause should exist for any given event ontologically. Here I speak of perfect clockwork, from beginning to end.

            Yes it could be that I’d be a pilot-wave supporter if I understood it. Nevertheless I am intrigued by the idea that non time or space dimensions exist which account for the spookiness that we observe. (Not sure if anyone influential is proposing this.) Note that if there are dimensions to existence which join matter at the quantum level in ways that we don’t otherwise perceive (as seems to be observed in quantum entanglement for example), then space and time should tend to be subverted. And if any of these further dimensions foster causal function as well as the ones that we know of, then certainty might exist ontologically even if we have no clue about what was going on.

            I highly suspect that SR, GR, and all humanly fabricated theories about what’s real, are not fundamental. Well except for “I think, therefore I am”. This is the one belief that I don’t mind stating in an ontological capacity.

            Liked by 1 person

          8. Eric,
            So, even if it’s stochastic, but emergent patterns and regularities can be identified, enough that we can make predictions reliable enough to build technology on them (which actually is the case with QM), would you still consider that supernatural? If so, consider the device you’re using to read this. It uses quantum physics.

            Extra dimensions would be an added assumption (or assumptions if we need multiple). They might turn out to be reality, but I’m not aware of any evidence for them yet.

            I do agree that it’s a very real possibility that none of our theories are fundamental.

            Liked by 1 person

          9. Yes Mike, I would call stochastic dynamics which nevertheless yield regularities, “supernatural”. In truth, from a deductive standpoint I don’t know how it would be possible for something which is truly random to also produce regularities. Wouldn’t that be false by definition? Anyway if truly random, and thus non-causal dynamics do create regularities in our world (despite the mentioned logical hurdle), by definition there would still be nothing which causes each specific event to occur as it does. Anything not accounted for in a causal capacity would thus be tagged as “supernatural” in an ontological capacity. This is to say that it wouldn’t be possible for anything to grasp why such an event occurs since no causal chain “of this world” would exist. So here there could be a god which is responsible, or nothing at all, though either way I’d call it “magic”.

            It seems to me that the fact that QM itself provides a useful platform for computation, let alone that causal dynamics seem to emerge from it, that this should exist by means of causality that we don’t yet and may never understand. Earlier you mentioned that we should keep trying to understand rather than throw our hands up from the “it’s ultimately magic” perspective. But it seems to me that this is what “stochastic” reduces to when considered ontologically, or a true void in causality.

            Liked by 1 person

          10. I am sympathetic to your response here Eric. Here’s my final analysis: If it can be demonstrated that a theory within the classical world such as General Relativity with its mystical, magical fabric of space/time is a bullshit story, why should one give any kind of credence to a story derived from a quantum world which cannot be seen. In the classical world, we can see the objects, measure those objects, and test those objects and yet, in spite of all of that access we still can’t get the theory right……. I’d say we’re pretty well fucked.


            Liked by 1 person

          11. I don’t consider us fucked Lee. It seems to me that science is still a relatively new institution. But once we develop a community of respected professionals with generally accepted principles of metaphysics, epistemology, and axiology from which to guide it, much greater progress should be made. This should mainly help traditionally soft varieties such as psychology, though apparently today even physics needs such help. I can’t say enough about the work that Sabine Hossenfelder is doing in this regard.


          12. Give me a break Eric…… From what I’ve seen and personally experienced, Sabine Hossenfelder is one of the most outrageous bigots I know of who runs a blog-site. Censorship is her fundamental mode of operation. I recommend swinging by Target and picking up a kerosene lamp, maybe you can rub that baby and some unbiased, un-bigoted, unprejudiced professionals will pop into existence with whom you can form an exclusive club to lead us…


            Liked by 1 person

          13. If she’s a bigot Lee, then I must not notice this because I tend to see things the way she does. But censorship? I haven’t noticed that whatsoever. She not only permits people to challenge her, but expends far more time ripping them up than I’d have the patience for in her shoes. Do you know of anyone that she’s blocked from commenting at her site? Who does she censure?


          14. Yours truly dude….. About a year and a half ago, I challenged her bigoted, disrespectful critique of Philip Goff, an exchange that between the two of them was quite heated, so she must know who I am. That’s one of the backlashes of blogging, one’s name shows up all over the internet. It’s a real privacy sort of thing…


            Liked by 1 person

          15. I don’t know Lee, saying that she must know who you are on that basis, seems presumptuous to me. There are a hell of a lot of people who comment over there. She does read all commentary before approval, apparently because things otherwise get out of hand. I think she recently tried to unburden herself of this chore through a new section where people can discuss things amongst themselves without her guidance. Regardless, on her site itself, law and order does seem required. And I have noticed her to let through all sorts of criticism. But if you’d like to provide us with a sample of one of your rejected comments, I’m sure that Mike would let it through.

            If I recall this right, she was late to the game on panpsychism. I believe it was only a few years ago that she wrote a post which began something like, “I’ve just learned that there are people who believe that everything is conscious!” So I can imagine her getting into it with Goff. As you know, I don’t consider this trendy panpsychism thing to solve anything.


          16. Eric,
            I read remarks posted on other blog-sites where individuals have been censored by Sabine. Censorship is a powerful tool used for the sole purpose of control. Just by the simple fact that Sabine filters every single comment before it gets posted demonstrates to me she is a control freak. Regardless of her shortcomings, Sabine does display some basic common sense approaches to science, even though in practice she has a tendency to resist her own advice. Resisting one’s own advice if it does not serve one’s own self interest is called a “double standard”.

            The one position I am full agreement with is her criticism of the predictive power of a theory or the math, in contrast to a theories explanatory power. She believes that the explanatory power of a theory should take precedence and supersede it’s predictive power. The justification for that reason is quite simple, math does not prove a theory reflects the true nature of reality whereas, explanatory power corresponds to universal rules of logic, rules that are fundamentally based upon consistency where there are no exception, contradictions and or paradoxes.

            No offense Eric, but I find this statement of yours to be quite short sighted: “…I don’t consider this trendy panpsychism thing to solve anything.” And here is why. If you’ve been following my posts with Mike, you’ve seen that my explication of consciousness being universal is an opportunity for unprecedented explanatory power, especially when it comes to the process of evolution and natural selection (and please don’t forget that evolution is a process and not a “thing-in itself”).

            Here’s the compelling question: Just what is “natural selection”, exactly. The institution of science won’t explicitly answer the question, they out right ignore the question. The only reason the term was invented in the first place is to circumvent the notion of some form of teleology. It’s an intellectual maneuver to avoid the notion of a God of sorts, the supernatural or whatever one wants to call it. It’s a psychosis Eric, nothing more.

            Here’s the thing, we know consciousness exists, and that with our own experience with consciousness, we know that we have a limited degree of self-determination within an otherwise deterministic physical system. And what does that limited degree of self-determination do? It provides a venue through which diversity, novelty and uniqueness are expressed. That is the very definition of natural selection therefore, consciousness, with its limited degree of self-determination is the driving force behind the “process” of evolution, the very “process” of natural selection.

            That my friend, is explanatory power. Can you imagine sitting in a seventh grade science class and having evolution and the process of natural selection explained that way. You don’t have to respond to this post Eric, I’m just thinking out loud today.



  7. I don’t think I’ve seen the different competing interpretations of quantum physics summarized so well. And this basically lines up with my understanding of the current state of quantum physics. We have a bunch of math that seems to work well enough, but no one can agree on how to interpret that math in “real” world terms.

    Liked by 1 person

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