I’ve been thinking lately about quantum physics, a topic that seems to attract all sorts of crazy speculation and intense controversy, which seems inevitable. Quantum mechanics challenges our deepest held most cherished beliefs about how reality works. If you study the quantum world and you don’t come away deeply unsettled, then you simply haven’t properly engaged with it. (I originally wrote “understood” in the previous sentence instead of “engaged”, but the ghost of Richard Feymann reminded me that if you think you understand quantum mechanics, you don’t understand quantum mechanics.)
At the heart of the issue are facts such as that quantum particles operate as waves until someone “looks” at them, or more precisely, “measures” them, then they instantly begin behaving like particles with definite positions. There are other quantum properties, such as spin, which show similar dualities. Quantum objects in their pre-measurement states are referred to as being in a superposition. That superposition appears to instantly disappear when the measurement happens, with the object “choosing” a particular path, position, or state.
How do we know that the quantum objects are in this superposition before we look at them? Because in their superposition states, the spread out parts interfere with each other. This is evident in the famous double slit experiment, where single particles shot through the slits one at a time, interfere with themselves to produce the interference pattern that waves normally produce. If you’re not familiar with this experiment and its crazy implications, check out this video:
So, what’s going on here? What happens when the superposition disappears? The mathematics of quantum theory are reportedly rock solid. From a straight calculation standpoint, physicists know what to do. Which leads many of them to decry any attempt to further explain what’s happening. The phrase, “shut up and calculate,” is often exclaimed to pesky students who want to understand what is happening. This seems to be the oldest and most widely accepted attitude toward quantum mechanics in physics.
From what I understand, the original Copenhagen Interpretation was very much an instrumental view of quantum physics. It decried any attempt to explore beyond the observations and mathematics as hopeless speculation. (I say “original” because there are a plethora of views under the Copenhagen label, and many of them make ontological assertions that the original formulation seemed to avoid, such as insisting that there is no other reality than what is described.)
Under this view, the wave of the quantum object evolves under the wave function, a mathematical construct. When a measurement is attempted, the wave function “collapses”, which is just a fancy way of saying it disappears. The superposition becomes a definite state.
What exactly causes the collapse? What does “measurement” or “observation” mean in this context? It isn’t interaction with just another quantum object. Molecules have been held in quantum superposition, including, as a new recent experiment demonstrates, ones with thousands of atoms. For a molecule to hold together, chemical bonds have to form, and for the individual atoms to hold together, the components have to exchange bosons (photons, gluons, etc) with each other. All this happens and apparently fails to cause a collapse in otherwise isolated systems.
One proposal thrown out decades ago, which has long been a favorite of New Age spiritualists and similarly minded people, is that maybe consciousness causes the collapse. In other words, maybe it doesn’t happen until we look at it. However, most physicists don’t give this notion much weight. And the difficulties of engineering a quantum computer, which require that a superposition be maintained to get their processing benefits, seems to show (to the great annoyance of engineers) that systems with no interaction with consciousness still experience collapse.
What appears to cause the collapse is interaction with the environment. But what exactly is “the environment”? For an atom in a molecule, the environment would be the rest of the molecule, but an isolated molecule seems capable of maintaining its superposition. How complex or vast does the interacting system need to be to cause the collapse? The Copenhagen Interpretation merely says a macroscopic object, such as a measuring apparatus, but that’s an imprecise term. At what point do we leave the microscopic realm and enter the classical macroscopic realm? Experiments that succeed at isolating ever larger macromolecules seem able to preserve the quantum superposition.
If we move beyond the Copenhagen Interpretation, we encounter propositions that maybe the collapse doesn’t really happen. The oldest of these is the deBroglie-Bohm Interpretation. In it, there is always a particle that is guided by a pilot wave. The pilot wave appears to disappear on measurement, but what’s really happening is that the wave decoheres, loses its coherence into the environment, causing the particle to behave like a freestanding particle.
The problem is that this interpretation is explicitly non-local in that destroying any part of the wave causes the whole thing to cease any effect on the particle. Non-locality, essentially action at a distance, is considered anathema in physics. (Although it’s often asserted that quantum entanglement makes it unavoidable.)
The most controversial proposition is that maybe the collapse never happens and that the superposition continues, spreading to other systems. The elegance of this interpretation is that it essentially allows the system to continue evolving according to the Schrödinger equation, the central equation in the mathematics of quantum mechanics. From an Occam’s razor standpoint, this looks promising.
Well, except for a pesky detail. We don’t observe the surrounding environment going into a superposition. After a measurement, the measuring apparatus and lab setup seem just as singular as they always have. But this is sloppy thinking. Under this proposition, the measuring apparatus and lab have gone into superposition. We don’t observe it because we ourselves have gone into superposition.
In other words, there’s a version of the measuring apparatus that measures the particle going one way, and a version that measures it going the other way. There’s a version of the scientist that sees the measurement one way, and another version of the scientist that sees it the other way. When they call their colleague to tell them about the results, the colleague goes into superposition. When they publish their results, the journal goes into superposition. When we read the paper, we go into superposition. The superposition spreads ever farther out into spacetime.
We don’t see interference between the branches of superpositions because the waves have decohered, lost their phase with each other. Brian Greene in The Hidden Reality points out that it may be possible in principle to measure some remnant interference from the decohered waves, but it would be extremely difficult. Another physicist compared it to trying to measure the effects of Jupiter’s gravity on a satellite orbiting the Earth: possible in principle but beyond the precision of our current instruments.
Until that becomes possible, we have to consider each path as its own separate causal framework. Each quantum event expands the overall wave function of the universe, making each one its own separate branch of causality, in essence, its own separate universe or world, which is why this proposition is generally known as the Many Worlds Interpretation.
Which interpretation is reality? Obviously there’s a lot more of them than I mentioned here, so this post is unavoidably narrow in its consideration. To me, the (instrumental) Copenhagen Interpretation has the benefit of being epistemically humble. Years ago, I was attracted to the deBroglie-Bohm Interpretation, but it has a lot of problems and is not well regarded by most physicists.
The Many Worlds Interpretation seems absurd, but we need to remember that the interpretation itself isn’t so much absurd, but its implications. Criticizing the interpretation because of those implications, as this Quanta Magazine piece does, seems unproductive, akin to criticizing general relativity because we don’t like the relativity of simultaneity, or evolution because we don’t like what it says about humanity’s place in nature.
With every experiment that increases the maximally observed size of quantum objects, the more likely it seems to me that the whole universe is essentially quantum, and the more inevitable this interpretation seems.
Now, it may be possible that Hugh Everett III, the originator of this interpretation, was right that the wave function never collapses, but that some other factor prevents the unseen parts of the post-measurement wave from actually being real. Referred to as the unreal version of the interpretation, this seems to be the position of a lot of physicists. Since we have no present way of testing the proposition as Brian Greene suggested, we can’t know.
From a scientific perspective then, it seems like the most responsible position is agnosticism. But from an emotional perspective, I have to admit that the elegance of spreading superpositions are appealing to me, even if I’m very aware that there’s no way to test the implications.
What do you think? Am I missing anything? Are there actual physics problems with the Many Worlds Interpretation that should disqualify it? Or other interpretations that we should be considering?
SelfAwarePatterns 
There is no such thing as objectivity. Not all physicist dismiss some interaction with consciousness. Some very prominent physicists at least think its a plausible possibility. I love how folks want to dismiss any quantum connections to consciousnesses as mysticism. One has to wonder what would ever be enough evidence to at least get those who don’t want to give credence to at least say its plausible. They so easily accept Hawking’s many worlds and parallel universe hypotheses even though thus far no real method to test them exists either. But suggests that perhaps consciousness is more than the body and your a mystic. I like Penrose’s Biocentrism ideas. But I like others to include perhaps its an illusion or we live in a real matrix. But I certainly don’t consider myself a mystic.
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Hard not to arrive at that conclusion. If consciousness is a factor, then surely it lends support to a simulation. How, though, to test it?
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Matthew,
I appreciate your comment. What would you say is the evidence for consciousness causing the collapse?
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Well Im not as learned as you so I would say what is the evidence for it not causing the collapse? Testable verifiable evidence? Just like several hypotheses in quantum Physics testable, repeatable and verifiable evidence is often out of reach. I’m not saying anything is absolutely true but to dismiss a hypothesis out of hand when your preferred solution is just as untestable and unverifiable is not objective and not fair. In the end all of it might be wrong. If consciousness is merely something that fades after the death of the organism so be it, nothing we can do its natural law in that case. But until we know, if we can know, we should at least aknowledge some very smart Physicist do indeed think consciousness may play a role. Roger Penrose is no crazy person nor is Stuart Hammerhoff an uneducated loon. Those are just two people who have a wide variety of hypotheses that say its plausible that consciousness interacts with exotic quantum particles. Many point out the double slit Experiment among other things as an example of what might be. Nobody knows what is as of yet but to call legitimate scientists mystics for saying maybe is just unfair. In the end you and scientists like you might indeed be right but until its proven please give all legitimate scientists the same respect you gave Hawking when he proposed String Theory and all the craziness, parallel worlds, many copies of me on parallel worlds, and all the other things I watched on The Scifi Channel, that come with it. Now some scientists are saying consciousness is an illusion and that’s funny really. When you cant solve it say it doesn’t exist solves the problem only it doesn’t because it does exist only its nature is a mystery
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I think this is a very fine presentation/overview of quantum mechanics and its puzzles. Snappy title to the essay too!
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I agree.
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Thanks Mark!
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To the very limited extent that I understand the mathematics of decoherence, it does seem to make Everett the most natural interpretation. Why should orthogonal states just vanish when their effect on us diminishes? “Us” meaning the states of observers whose device registered a particle going through the left slit, for example, and “orthogonal ” meaning approximately orthogonal, to within some rounding error.
The fact that decoherence is in principle a smooth process, albeit a fast one, takes a lot of the sting out of the Many Worlds label. It’s kind of a misnomer. It would be equally fair to say there’s one world in Everett, but many superposed states that have extremely weak interactions.
A good resource is the wiki article on decoherence. Another is David Wallace, The Emergent Multiverse .
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Thanks for the references. I agree on the wiki article. I’ll check out the Wallace one.
Good point about the label. The main reason I described MWI the way I did was to downplay the new universes thing. Dewitt reportedly used it as a selling tool, but I think it makes too many people dismiss it as outlandish without understanding what’s actually being proposed.
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Nobody knows the source or nature of consciousness. There is evidence you remain conscious after the heart stops and blood flow to the brain ceases. For how long is still being examined. Previously this was not thought possible. Now some adjust there position saying activity continues till clinical brain death. No one as of yet can provide evidence consciousness is not affecting quantum particles or the double slit Experiment because nobody knows the nature, origin, components or make up of consciousness. Hell some just give up altogether and say its not real anyway, its an illusion. So all human beings are, what they have acomplished over millions of years of evolution is an illusion. Anyone who matter of factly claims they can prove consciousnesses is not affecting the quantum relm or vis versa know there wrong. Nobody even knows what consciousness is composed of let alone its origins so they can’t say for sure one way or another. They can dismiss it as woo or mysticism, they can belittle those who at least say maybe but, just like those who subjectively hope consciousness doesn’t die, they cant prove anything one way or the other. I wouldn’t be so harsh if people disparage brilliant scientists like Penrose and others by calling it mysticism. No better way to disparage a scientist than to call his or her hypothesis mysticism. Nobody called Hawking a mystic when ge hypothesized String Theory which is a parallel worlds theory with absolutely no direct evidence of it being true. Honestly parallel universes with my double in them sounds pretty darn mystical to me.
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Don’t confuse the scientific method with the actual scientists. Scientists are people, human beings, and like all human beings they are almost incapable of objectivity on there own. If you can pick it up, put it in a beaker, and test it using the Scientific Method thats objective. Supposedly if the math works that is a good sign it could be true but even if tte math works it still can be wrong. If you can’t pick it up and test it it could be wrong. Quantum Physics reaches out into a largely untestable area of science. In fact many well known scientists ponder aloud that maybe we have reached or soon will reach all we are capable of knowing leaving infinite amounts of questions unanswered and unknowable.
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Hi Matthew,
“…I would say what is the evidence for it not causing the collapse? Testable verifiable evidence? ”
I alluded to some in the post: the difficulty in constructing a quantum computer. Quantum computing’s unique value is being able to process possible paths in parallel, which requires maintaining a superposition as long as possible. However, long before any conscious entity becomes aware of what’s happening, the superposition decoheres. This is a serious challenge for QC. If it could be overcome simply by keeping conscious systems from seeing it, it likely would have been solved decades ago. As it is, many QC processors have to operate at near 0 Kelvin to minimize interaction with the environment and even that only keeps the qubit circuits in superposition for a very brief time.
“Nobody knows the source or nature of consciousness.”
I think neuroscience is making steady progress in understanding it. (See the posts in my Mind and AI category for why.) Of course, many people don’t like what’s being found, so the assertion that science is utterly helpless in this area remains a popular one.
“Don’t confuse the scientific method with the actual scientists.”
A crucial part of scientific methods (there isn’t just one) is guarding against human bias. It’s why results must be repeatable, transparent, and subject to peer review. In my experience, the ones that pass this test don’t affirm expansive conceptions of consciousness.
But as you note, there is no unique evidence for any one interpretation of quantum physics. It’s why I said that the responsible position is agnosticism on them. For now.
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Maybe a little beside the point … Please forgive me.
As someone who could not even bother with elementary school and for several years has not been able to master English … he claims that scientists do not understand the basic processes of the universe.
Well, it can be said, it’s just a stupid Pole.
But I will not be giving hundreds of examples of scientific indolence. Only one.
Just what to think of the state of the scientific mind, when one of the most prominent minds, carries out such a thought experiment … whether it was just a joke or just a word of despair
Throw a book into the black hole. The book carries information. Perhaps that information is about physics, perhaps that information is the plot of a romance novel – it could be any kind of information. But as far as anyone knows, the outgoing Hawking radiation is the same no matter what went into the black hole. The information is apparently lost – where did it go?
Do we see one of the greatest idiocys of quantum physics?
Do we see how beautiful minds are stupidity?
Maybe just a stupid pole is dumber than it would seem?
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Stan,
From what I understand, information lost to a black hole remains a problem that hasn’t been solved. I’ve read some speculation that maybe it’s smeared across the event horizon as a sort of hologram, which sounds like it could conceivably affect Hawking radiation, but it all sounds highly speculative.
One of the problems with physics today is that too much of the theoretical work happens far outside of testable conditions. On the one hand, this should be fine since we never know when such exploration might turn up something testable. But until it does, we have to be stringent in remembering that it’s informed speculation.
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Mike.
Only this is not a problem with the information that carries the object that falls into a black hole.
This applies to the information that the object carries about itself.
Is known that information is the basis of the quantum universe.
………..
1. Throw two stones into a black hole. On one we paint the flag US and the second flag of Poland.
Does such information mean something.
……….
2. Now we will fire two cannonballs towards the black hole.
A stone ball from Poland and a ball of uranium from the US.
………..
Is this the sense of information for quantum physics?
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Stan,
Sorry, you’ve gone beyond my knowledge on this. I don’t know enough about this to even speculate intelligently. Maybe someone more versed in the physics can answer.
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I can only support what you said earlier, that the Black Hole Information Paradox is an unresolved — and vexing — issue.
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Mike.
If I didn’t believe in your wonderful reasoning … after all, I read your wise statements.
If something is to blame, it is my tragic English.
Besides, the scientists themselves, although they are so wonderful in quantum physics, admit that they absolutely have no idea why this works.
so I disappear… but not on twitter.
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My problem with MWI is the same one many have: where do all those new realities come from? What does it suggest about matter and energy?
Tegmarkians can talk about how the square root of 4 is both +2 and -2, and no one worries about where the extra answer came from. But I don’t believe we live in a Tegmarkian universe.
There is also, to me, an issue of reality explosion: Wear a pair of polarizing sunglasses, and each photon that hits them has a chance of passing through or not. So each photon seems to be creating new realities. Billions and billions of new realities. Every instant.
MWI fans have said this doesn’t happen, but I’m not clear on why not.
I have played with the idea that what happens is that the standing wave of the universe becomes more complex with each possible branch such that all possible paths that could have been taken are part of that wave. But there’s only one actual reality that emerges from that wave.
I’ve never found the waveform collapse all that mysterious. A particle in flight is a vibration in the relevant particle field, the energy of that quanta is spread out in the wave. But for that energy to interact with, say, an electron in the wall it hits, that single spread out quanta “drains” into the contact point.
The mystery, if I understand it, has to do with what “selects” that contact point, and how does the energy of the wave “drain” into that point? We have no maths for that.
I suspect the contact point gets selected per the same mechanism that “selects” which atom of a radioactive sample decays next. Or as how the first bird of a flock decides to take to the air. Maybe it is literally random (which it seems to be).
I sure wish someone would discover something new. QFT and GR have been at loggerheads far too long.
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I have to admit that I wonder about the energy aspect of this as well. If every part of the wave becomes a full particle in its own branch of the superposition, then how is the energy of that wave, and every other wave, not effectively magnified? My understanding is that we still don’t understand at a fundamental level how mass is generated. (The Higgs supposedly only explains a subset of it.) If the non-visible parts of the post-measurement wave aren’t real, then maybe that has something to do with it.
What’s interesting about the explosion of superpositions, is virtually all quantum events average out until the macroscopic deterministic world emerges. To me, that implies that most of the “universes” being generated are virtually identical. (There would have been far more divergence in the early instances of the big bang when quantum events generated patterns that later grew into voids and galactic superclusters.) Today, it seems like it would only be the rare case of quantum indeterminancy “bleeding” through that would lead to divergences. It might be that most of the exploding superpositions end up converging back to one reality, or only a few of them. (I have no idea if the mathematics lend any credence whatsoever to just conjecture.) And I’ve read some variances of the interpretation that, instead of proliferating universes, it’s really just interacting ones.
“But for that energy to interact with, say, an electron in the wall it hits, that single spread out quanta “drains” into the contact point.”
That actually isn’t my understanding of what happens. As I understand it, the entire wave instantly disappears, replaced by the particle, even if the wave has been spread around and fragmented over vast distances, that there’s no timeline for it to drain. (Which admittedly also makes “collapse” a questionable word for the phenomenon.) That said, decoherence isn’t supposed to be instantaneous either, just very fast, so who knows.
Totally agreed that it would be good to see progress somewhere. I remember many physicists hoping the LHC would provide something, anything, unexpected so they’d have something to work with, but other than failing to confirm supersymmetry, most of what they’ve gotten just seemed to reaffirm the Standard Model.
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“My understanding is that we still don’t understand at a fundamental level how mass is generated. (The Higgs supposedly only explains a subset of it.)”
Yeah, the mass of protons and neutrons, for example, comes mainly from the energy of the quark and gluon interactions, which means most of the mass from matter isn’t due to the Higgs.
Which is why I find it easier to think about in terms of energy, although I usually see mass and energy as two faces of the same thing.
“To me, that implies that most of the “universes” being generated are virtually identical.”
Which I think is how MWI fans respond to the question about sunglasses and photons. My question in return is how identical is “virtually” identical?
Remember Bradbury’s famous short story, The Sound of Thunder? Do worldlines converge and merge, or do even quantum differences ultimately diverge and result in separate realities?
A lot of MWI fans think Occam and parsimony support their position, but I (so far) see it the opposite. MWI doesn’t sound like the simple explanation, and the explosion problem defies parsimony.
But then I’m not sure I truly understand MWI, and I’ve gotten the impression a lot of its fans don’t really understand it, either. Plus, there seem to be multiple versions of the theory since Everett.
Greg Egan has a short story, The Infinite Assassin, in his collection, Axiomatic. It’s about an illegal drug that allows users to interact with parallel universes, which turns out to be a Very Bad Thing. What I really liked about the story was the sense of continuum Egan gives to parallel worlds.
“And I’ve read some variances of the interpretation that, instead of proliferating universes, it’s really just interacting ones.”
One can’t help but wonder what makes them distinct.
Sean Carroll gave a talk about MWI (which I found unconvincing), and he had an experiment set up remotely that did a photon-half-silver-mirror thing with two detectors. Through a phone app he was able to trigger the experiment and get a (random) result which he used to determine if he should jump to the left or to the right. (The right, in this case, IIRC.)
The claim was that this generated two realities accommodating his jumping both ways. Which generated two different audiences (and sets of video viewers) who remember him jumping both ways. Which led to this comment where I recall him jumping right. Presumably the alternate me remembers it differently.
But I keep wondering about those sunglasses and all the quantum interactions happening all the time. I’ve just never heard anything from MWI that gets me past this key objection.
“As I understand it, the entire wave instantly disappears, replaced by the particle, even if the wave has been spread around and fragmented over vast distances, that there’s no timeline for it to drain.”
Yes, agreed. (That’s why I quoted “drains” — best word I could think of but hardly adequate.) I think we’re on the same page here, I’m just trying to imagine an ontology that makes sense of “waveform collapse.”
I’ve been thinking about this a bit as I try to wrap my head around some of the strange variations of the two-slit thing. (Have you see the three-slit experiment? Mind-blowing!)
In a single photon event, the laser emits a “photon” with no location but a wave (with momentum) that expands from the laser into the surrounding environment. It’s a single quanta of energy causing a vibration in the EM field.
Now that energy has to go somewhere, and what we see happening is that waveform somehow interacting with some electron in some atom such that the electron is raised to a new energy level. At that point, the photon does have a location (and presumably we can no longer talk about its momentum).
That interaction requires the full energy of the quanta, so the energy in the field “goes” (or “drains” or some better word) into that interaction.
But this is just me pondering the “waveform collapse” issue and WAG-ing at an ontology.
“I remember many physicists hoping the LHC would provide something, anything,”
Yeah, and now it’s shut down for two years for an upgrade. You’d think not finding SUSY at all would take the wind out of certain sails, but they just keep redefining the target. Part of the problem is that String Theory seems to need it, so no SUSY threatens ST.
There’s also that chart you’ve probably seen showing how the three forces unify at very high energies? Those curves intersect at the same point only if SUSY is true. Without SUSY, they don’t.
So it’s a dream that’s hard to kill.
There was some hope of seeing something new in very esoteric sectors involving (IIRC) weak decay. I can’t recall what it was exactly, and no one is jumping up and down, so whatever they saw may have not survived more analysis. They were seeing bumps in both CMS and ATLAS, I think, and combining the two bumps gave them a nice sigma, but the data weren’t compatible so combining them didn’t really say anything.
Or something like that.
Merry Christmas!
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“My question in return is how identical is “virtually” identical?”
My conception is that normal events, such as all the deterministic events we see in nature where the quantum events average out, don’t create deviations. It’s only when we tie a macroscopic event to a specific quantum outcome, that a notable divergence happens. As you note, even a minor “meaningless” macroscopic event (such as which way Carroll jumped) might eventually butterfly into major changes.
Of course, we can’t rule out the possibility that quantum indeterminacy doesn’t “bleed” into the macroscopic world outside the precision of our instruments and butterfly all on its own, so the idea of similar universes may not be tenable.
There are definitely lots of versions in the Everettian family of interpretations. One I recently heard about on the Rationally Speaking podcast was relational quantum mechanics, which posits that whether a wave has decohered is relative to an observer. In other words, like the relativity of simultaneity in Einstein’s theories, this holds that where you are in the sequence of events determines when you see the collapse. Schrodinger’s cat sees the collapse as soon as the detection device is triggered, but Schrodinger himself doesn’t see it until he opens the box. However, the relational interpretation is reportedly agnostic about the reality of the other outcomes. (It doesn’t seem agnostic to me, but I probably don’t grasp the full idea.)
I need to look up that Egan story. It sounds interesting.
Ah, ok, I missed the quotes on “drain.” Thanks for the description of the photon. Part of what I find interesting about this is that the electrons are presumably constantly exchanging photons with each other and the nucleus, but despite that exhibit quantum waveness to those of us outside the relationship, which makes me think of the relational interpretation again.
I don’t think I knew that uniting all three forces required SUSY. Interesting. I know the weak and electomagnetic one were already shown to be the same. (Which strikes me as an odd pair.)
All in all, I think I’m happy I’m not a physicist right now.
Merry Christmas!
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“It’s only when we tie a macroscopic event to a specific quantum outcome, that a notable divergence happens.”
That matches what I’ve heard from MWI fans, but it seems to suffer the same micro/macro issues as many quantum things do. What is a “notable divergence” and what happens? Reality doesn’t diverge at all (why not?), or the diverged lines merge into one (again, why?).
That Egan story is good at pointing out how, if we take MWI at face value, our own reality is a fuzzy continuum of indistinguishable nearby realities. At what point am “I” no longer really me?
Chaos theory suggests (to me) that even minute differences may result in large changes down the road. What if, butterfly fashion, a photon that did pass through my sunglasses accounts for some minute change that ultimately destroys Saturn?
I’ve long wanted to sit down with a working theoretical physisict who’s really into, has really studied, MWI, because I’d like to understand how people like Sean Carroll identify MWI as their preferred interpretation. Some even say it’s the mostly glaringly obvious interpretation!
“In other words, like the relativity of simultaneity in Einstein’s theories, this holds that where you are in the sequence of events determines when you see the collapse.”
Doesn’t part of that thinking also come up in Copenhagen? The idea that the cat isn’t superposed to itself, but is to the scientist who hasn’t opened the box. Likewise, the science writer standing outside the lab is superposed until the scientist informs them of the result. And millions of readers are superposed until they read the writer’s article. (And everyone in Andromeda remains superposed probably forever.)
I’m not sure I believe in the idea of macro objects being superposed. What does it mean to suggest I’m superposed? Can experiments demonstrate it? Or is it just that I lack knowledge?
Ugh. We really need some advances in HE physics. We’re just grasping in the dark here.
“Part of what I find interesting about this is that the electrons are presumably constantly exchanging photons with each other and the nucleus, but despite that exhibit quantum waveness to those of us outside the relationship, which makes me think of the relational interpretation again.”
I think at least some of that is accounted for in the difference between virtual photons and actual photons. I’ve seen some physics videos recently emphasizing the difference between them and how you can’t treat virtual photons as real — they’re almost an accounting device, although obviously something physical is going on. Lamb shift and so forth.
“I know the weak and electomagnetic one were already shown to be the same. (Which strikes me as an odd pair.)”
Same here! Electro-weak theory. (And the weak force is the one many books hand-wave on that “has something to do with radioactive decay” … yeah, and making the sun work, too!)
It sure made it seem like unification was a thing though, didn’t it. If two things as seemingly different as EM and weak force are unified, why not the strong force?
Again, we need more information! We don’t even really know if gravity is a force!
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“At what point am “I” no longer really me?”
Michael and I discussed this as well somewhere else on this thread. It seems like reality likes ruining our clean little categories, such as what is life or non-life (see prions or viriods), what is the border between species (some members of species A can mate with species B, but others can’t), what is computation, or what is a planet. It won’t surprise me too much if it scrambles our ideas of the self.
“What if, butterfly fashion, a photon that did pass through my sunglasses accounts for some minute change that ultimately destroys Saturn?”
I told you to stop playing with those glasses Wyrd! Now look at what you’ve done. Who’s going to clean up this mess? We’ve got Saturn all over everything! 🙂
I recently went back and read Sean Carroll’s blog post on the MWI. I’m not sure his instincts on explaining it are the best. He tends to emphasize the multiple universes thing, which I think is a mistake. http://www.preposterousuniverse.com/blog/2014/06/30/why-the-many-worlds-formulation-of-quantum-mechanics-is-probably-correct/
Paul Torek above recommended David Wallace’s ‘The Emergent Multiverse’, which I’m thinking about picking up. It looks pretty good in the preview. My only pause is it’s pricey. Of course I’ve often spent more on neuroscience books. I just have to decide if I’m interested enough and willing to invest the work it would require.
I can see why people say the MWI is the most straightforward interpretation though. It does explain a lot. I see it as a candidate for reality. The only question is whether the implications of it in any way falsify it. But as I commented on Carroll’s post, that’s the problem with these interpretations. None of them are uniquely testable.
“— they’re almost an accounting device, although obviously something physical is going on. ”
Didn’t quantum physics start with Max Planck introducing a quanta purely as an accounting device? There was a similar disclaimer on Copernicus’ book. It seems like a lot of physics starts with someone saying, “Don’t worry, this is only for calculating convenience. It’s not it’s real or anything.”
“Again, we need more information! We don’t even really know if gravity is a force!”
Totally agreed on needing more information. Although wouldn’t you say we know gravity is a force? Or did you mean if it’s a force like the others in the Standard Model, with bosons (gravitons) and the like?
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“It won’t surprise me too much if it scrambles our ideas of the self.”
Yeah. The more I learn and think about “the self” the more complex and puzzling it seems.
“[MWI] does explain a lot.”
That I do realize. I’m confounded by the whole multiple universes thing; that’s pretty much the entirety craw stick.
I vaguely remember reading that Sean Carroll post. Think I’ll go back and re-read it this evening.
The Wallace book sounds kinda interesting… once I read about it. The title put me off, because while I’m open-minded-but-skeptical on MWI, I’m disbelieving (and disinterested) in multiverse theories. I found an online review of the Wallace book that sounds like another read for this evening.
“Didn’t quantum physics start with Max Planck introducing a quanta purely as an accounting device?”
Ha, yes, good point!
“Or did you mean if [gravity is] a force like the others in the Standard Model, with bosons (gravitons) and the like?”
Exactly. I want GR to be essentially correct with some minor correction to accommodate quantum, and I want QFT to turn out to be essentially epicyles — a theory that matches our instruments but is seriously wrong in some key regard.
We know matter/energy is quantized, but the jury is out on time/space. I want them to be smooth (providing yet another duality to reality). And that gravity is due to warped spacetime and there is no such thing as a graviton.
My spacetime wishlist. 😀
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Wow, that review is 19 pages long. I thought I might sneak a quick read before responding, but I think I’ll just add it to my queue too. Thanks for linking to it!
On GR and QM, I don’t really have preferences on which one wins (assuming they both don’t eventually have to be heavily modified). If spacetime does appear to be smooth, I wonder if we could ever be sure it wasn’t quantized at a size below the level of precision of whatever we were using to measure it.
And an infinitely divisible spacetime seems like it would come with its own potential multiverses. If the space between elementary particles is infinitely divisible, it allows patterns to exist there below our notice, such as entire micro-universes. And entire other universes could have been born, existed, and died in the Planck time at the beginning of the big bang. For that matter, an infinity of universes might have existed during the time you read this reply. (Don’t hit me.)
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I gave up (for now) on that review once I got to the discussion section. They were a little too glowing in their assessment for me to trust, and there was already a bit of a “yelling at the screen” thing going on here on the material they mentioned to that point.
The book does sound interesting, though. I found myself wondering if Wallace explains some of the stuff that was making me yell.
Continuous spacetime does seem to have the same weird issues the real numbers have. Maybe matter/energy being quantized saves the day?
While space might be infinitely small, matter isn’t, so no micro-galaxies hiding in the dust motes. Quantum limits on energy might also affect the minimum time it takes anything to happen (like c limits causality).
The question might be whether we can trust scale. Atoms have sizes due to their properties, so maybe certain things can only happen on certain scales. (And we use atomic vibrations to define the second.)
Or maybe they’ll find a graviton (or a chronon), and that will end the matter. But until then… well, just say that I look at GR and think, yes, that makes sense, but look at QFT and think, wait, what?!
Obviously the universe is under no obligation to fulfill my sense of how it ought to behave (oh, if only). 🙂
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“While space might be infinitely small, matter isn’t, so no micro-galaxies hiding in the dust motes.”
I actually wasn’t thinking the micro-universe patterns would be made of any matter/energy as we understand it, but something else, something we never see because it exists too far below the scales we can detect. Call it Mini-Me matter which could have it own smaller Mini-me quanta sizes. Of course, between Mini-Me matter might be Mini-mini-Me matter, and so forth and so on. Turtles all the way down.
Or if in fact there is only the matter/energy we’re familiar with, that means an infinite emptiness between every occurrence of it, which would itself be profound.
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Yes, as profound as the next real number after zero!
Talk about macro objects in superposition… I’m totally superposed on the real numbers being, in fact, real or, as sure seems sometimes, a fabrication of our imagination.
The thing is: how real is a circle, its diameter, and their ratio? If they are real, so is pi.
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I don’t get the whole ‘measuring changes quantum particles behavior’ thing. And by ‘not get’ it seems like it doesn’t work or is a simplification that lost important details on the way. For example if ‘measuring’ changes the quantum particles, then at what distance can you measure them? Any distance? If so wow, you’ve invented an instantaneous communication device that’s…faster than light. Nice. Or if the distance actually matters, then ‘measure’ is a term that is a heuristic and lacks the actual details like what distances are involved and where does the effect run out?
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You’re totally right not to get it. “Measurement” or “observation” is a maddeningly vague aspect of this. It reflects the lived experiences of scientists running experiments on quantum phenomena. Niels Bohr reportedly insisted that the description of this be limited to “ordinary” language, presumably because any attempt at a more precise description would imply knowledge we don’t really have.
It’s called “the measurement problem,” and it’s at the heart of the absurd nature of quantum mechanics. Attempts to solve it have led people down all kinds of bizarre paths.
I sometimes think QM represents the limits of our reality, where that reality emerges from some other underlying meta-reality. It might be that any “interpretation” is simply a vain attempt to map that meta-reality back into our little parochial reality. As patterns in and of the parochial reality, we simply may not be equipped to understand the wider meta-reality.
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FWIW, I see “measurement” as anything that resolves superposition. For me, the cat was always (obviously) either alive or dead, because the detector monitoring the radioactive sample is the measurement. There is no superposition; there is only a lack of knowledge about the cat.
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Excellent post, Mike. I enjoy mulling these quantum conundrums around. I am left feeling like an extremely poor sommelier of ideas–I get hints of different flavors but… really I have no idea what I’m tasting. It’s just really, really complex and intriguing. My own opinion is that we just don’t really know what we’re studying, and that at some point there will be a breakthrough in our conception of what reality actually is that will assist us in fitting the pieces of the puzzle we’ve found so far into a more insightful framework. As an example, I think our notions of physical and non-physical have pretty much broken down, and we have only vague ideas as to what consciousness might be, most of them extremely myopic, so that we’re in the position of using pretty poor tools for the job.
Just as one example, in that Quanta article to which you linked, Brian Greene suggests that each copy of you in the MWI is really you, and that the true you is the sum total of these you’s. Something like that. When a scientist says that a “self” might be a superposition of conscious selves occupying subtly related windows of reality, it’s an interesting idea to some folks and frowned upon by others–while when the classic New Age book Seth Speaks posits the same notion it is deemed woo woo foo foo to that crowd, but accepted by the other. This is, in a sense, what I mean about once clear concepts and divisions breaking down. So my own feeling is everyone’s a little bit right, and the answer is somehow a superposition of a great many ideas out there… 🙂
I don’t suspect a ton of physicists are lining up to endorse Brian Greene’s idea of the self. I have no idea, actually. But it’s always interesting to me when these parallels emerge. I think it’s safe to say whatever “models” or “conceptual frameworks” we use to try and organize our phenomenal observations are all wanting right now. What I dislike about the Copenhagen Interpretation is that it seems like a consequential moment in defining the purpose of science–which accepts setting aside questions about what the universe really is, and accepting as complete descriptions of what it does. For me, science is much less interesting when only one of the two questions remains in play…
Happy Holidays, Mike!
Michael
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Thanks Michael, and great hearing from you! Your comments are always thought provoking.
On Brian Greene’s notion of the self spanning multiple copies, I think, much like the notion of additional selves that originate from the idea of mind uploading, it’s a matter of philosophy, in other words, not a fact of the matter, but a personal choice. In both cases, the issue gets blurred as the copies get farther and farther away from the original.
For example, is someone born with my exact genetics, but due to an early quantum branching, lived a radically different life, still me? What about someone who branched away from me before I became a skeptic? Or even before I became interested in science? Or someone who branched away before I broke up with one of my old girlfriends, but instead married her and proceeded to have a large family?
My attitude is that these would all be a sort of sibling, albeit in the case of recent copies, far closer to me than any brother or sister. The only way I might be tempted to ever consider them to be me is if we could somehow share memories, but even then I’d expect difference to arise based on the order in which the various copies received the different memories.
On the Copenhagen Interpretation, I can understand not liking its inherent instrumentalism. I totally agree it’s a lot more inspirational to think of science as the pursuit of truth. The pursuit of models that accurately predict future observations…just doesn’t have the same inspirational resonance.
On the other hand, maybe the idea that the pursuit of truth is anything other than the pursuit of predictive models is an illusion. The real dividing line is whether we want to get into models that make predictions we can’t test. The Copenhagen Interpretation (apparently heavily influenced by the logical positivism in vogue during its formulation), labels that as undesirable.
I think by calling these models that go beyond the mathematics of quantum mechanics “interpretations”, physics has found a way to have its cake and eat it too. It allows us to label the predictive aspects of QM as settled science, but keep trying to figure out what it means.
Although as I’ve noted to you before, and as I did to Callan above, I sometimes wonder if quantum phenomena isn’t right at the edge of the reality we, as a subset of that reality, have any ability to make sense of. It might be a hole we can navigate around mathematically, but can never enter. (Although I hope we never stop trying.)
Happy Holidays to you too Michael!
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I have some strong opinions about this issue, and have been meaning to bring this up with Sabine Hossenfelder over at http://backreaction.blogspot.com/?m=1. So far I’ve been too shy however. This is a woman who I absolutely love! She’d like to help “fix” a physics community that seems to have gotten “lost in the math”. Similarly I’d like to help a science community that attempts to function without generally accepted principles of metaphysics, epistemology, and axiology (or the three elements of “philosophy”). Perhaps if I feel that I’m able to develop my QM ideas here well enough, then I’ll become confident enough to speak with her about this over there some time? Well maybe.
Rather than get caught up in all sorts of higher speculation initially, I like to begin with QM basics. We humans perceive matter in terms of “particles” and in terms of “waves”. Are such perceptions good enough? Apparently they are not. When we try to pin down the exact state of a particle we’re confounded with wave like characteristics. Then when we try to pin down the exact state of a wave we’re confounded by particle like characteristics. So it should instead be better to consider matter to function as both. But apparently we can’t measure matter as some kind of hybrid of the two. Therefore it makes sense to me that we’d witness fundamental uncertainty as expressed by Heisenberg’s uncertainty principle, or an inequality that references Planck’s constant.
So to me there isn’t too much to worry about here. If we must measure particles in one way and waves in another way, though matter ultimately functions as neither but both, then we should expect to be confounded by more exacting measurements in either regard. Given the circumstances, is this not logical?
For example, let’s say that we find a material that’s similar to both rock and wood. So if we assess it as a kind of rock then the harder we look at it from this perspective, the more confounding this stuff should seem to us. Or the same could be said if we assess it as a kind of wood. So that’s essentially what I’m saying is happening with our assessments of matter. If it’s effectively “particle-wave”, though we can only provide measurements in one way or the other, then we should naturally fail as our measurements become more precise. Thus I’m good with quantum mechanics as I understand it. Apparently we’re too stupid or whatever to understand what’s going on.
The controversy however seems to be that most physicists (unlike Einstein) haven’t been content settling for such human epistemic failure. So apparently they’ve decided that no, it’s not that we’re trying to measure something as particle or wave that’s neither. Instead it must be that the uncertainty associated with either variety of measurement reflects an ontological uncertainty which exists in nature itself! So the argument is not that we’re stupid, but rather that nature itself functions outside the bounds of causality, or thus nature functions “stupidly”.
It could be that this view is entirely correct, but what irks me here it is that these physicists also refuse to admit that they thus forfeit their naturalism. Apparently they want to call themselves naturalists, but interpreting QM such that nature functions without causality — well that ain’t natural!
It’s the borderlands of science, such as here, brain study, and so on, that seem most in need of effective principle of philosophy. For this issue I offer my single principle of metaphysics. It reads:
Unless I’m missing something this “Many worlds” interpretation appears in violation. I interpret it as physicists deciding that reality functions without causality (or “magically”), and then attempt to make sense of this anyway by theorizing “many worlds”. The more that we leave the bounds of causality behind, or thus introduce magical function, explanations should grow obsolete. From here reality should just be what it is. So I consider these sorts of interpretations of quantum mechanics to illustrate category error.
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A lot of your criticism seems aimed at the more ontological versions of the Copenhagen Interpretation, the ones that say that not only are we faced with an epistemic limit, but that there’s nothing else there, that reality isn’t set until the measurement. That’s usually the version of the CI that critics inveigh against, and I agree with that criticism. The ontological versions of the CI seem excessively pessimistic.
I think Neil Bohr’s version of the CI was closer to your sentiment. Here are the observations, and here are mathematics that can make predictions about those observations, with limitations, but within those limitations predictions are accurate enough to build technologies on top of them, so, “shut up and calculate!” I’ve grown to respect this view more as I’ve continued to learn about quantum physics. It’s not satisfying, but it’s at least epistemically humble.
But I think an MWI enthusiast would respond to you that their interpretation does restore determinism. Unfortunately, it’s determinism for reality overall, not a determinism we can observe. Which of course raises the question, if something is deterministic but not deterministic from any observer’s perspective, is that really deterministic? Who is it deterministic for?
One question I’d have for you is, how do you define naturalism? Is that definition mutable on new evidence? Myself, if I encounter phenomena that doesn’t meet my understanding of naturalism, I would still want to understand the phenomena as much as I could. But naturalism for me is just a set of working assumptions, ones subject to being adjusted as I learn more.
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If I may interrupt, two quick thoughts:
Firstly, I’m also a big fan of Sabine’s blog, been reading it for years. I highly recommend it. (Peter Woit also has a good blog.)
Secondly, just as (and I very much agree) physicists benefit from philosophy, philosophers can benefit from looking into some of the math involved. Quantum physics is highly mathematical, and the wave-particle duality confusion is, at least in part, a failure of language. At the math level, the confusion essentially goes away.
The way it’s usually put is that matter (as in particles) is something outside our direct experience that has wave-like properties and particle-like properties depending on what aspect of the particle one tests.
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Wyrd,
I was hoping to hear from you most of all! Perhaps on some level I mentioned Sabine because I recall you mentioning her another time? Anyway it was late 2015 that I became interested in her. Massimo Pigliucci had blogged about her position from a Munich physics conference that he attended.
On philosophers benefiting from math and physics, I certainly agree. I was initially most interested in philosophy as a university student, but didn’t want to become acclimated to accept no generally accepted agreements in the field. And beyond questions what could they teach me without generally accepted positions? Mental and behavioral sciences were next, though I found them far too speculative for comfort. So I looked for a field that could teach me how to learn. Yes physics! But alas, my own mind would not get me through upper division courses. I eventually earned a degree in economics, which I chose somewhat because it corresponded with my own amoral theory of value.
I didn’t mean to imply that modern physicists would improve if they were to become versed in modern philosophy. I actually believe that the field has tremendous problems, though needs improvement in order to better found science.
Regarding language, that’s one of my own main themes. So QM interpretations work pretty well mathematically? But I suppose that natural language explanations are needed most. Mathematics is many orders less descriptive than English. Notice that there’s nothing in mathematics which can’t be described in English, and yet much in English can’t be described in mathematics. Still the English interpretation of the mathematical QM interpretation that you’ve provided seems pretty close to mine.
Mike,
It’s good to hear that you oppose the ontological version of the Copenhagen Interpretation. Actually I was under the impression that Bohr’s interpretation was more ontological, though perhaps not. Did he ever support Einstein’s “I, at any rate, am convinced that He [God] does not throw dice.”? (Though in practice I support Einstein about that, my own metaphysics is a bit more pragmatic. It’s more like “To the extent that God throws dice, nothing exists to figure out anyway!”)
If Many World enthusiasts are truly causal determinists, then tell me this. Do you think their position holds that all of these worlds actually exist? As in ontologically exist? As a solipsist I can stomach all sorts of crazy notions from a supernatural premise. But in a causal sense that position seems utterly ridiculous. Conversely if these many worlders are simply going epistemological with their position, as in “It can be helpful for us to think about QM this way…” then I could give their position some reasonable consideration.
Yep Mike, it’s deterministic. Who for? All that exists. Once again, I’m a solipsist. Reality is reality regardless of the human’s various idiotic notions.
I define naturalism as a belief that reality functions causally in the end. This definition is a definition, and therefore isn’t mutable to new evidence. Even if I ultimately decide that reality does not function causally, I should still consider this to be a useful definition. Here I’d either be a supernaturalist, or a hypocrite that changes my definition in order to call myself a naturalist.
I understand the desire to understand. This seems quite human and adaptive. Even the most faithful god fearing person should need to use reason in his or her life in order to get along. But to the extent that causality fails, as in ontological interpretations of the uncertainty associated with Heisenberg’s principle, things should not exist to figure out anyway.
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Eric,
Bohr very much did not support Einstein in his statement about God not playing dice. His response was along the lines of, “Einstein, don’t tell God what to do.” Honestly, while I think his and Heisenberg’s initial strategy was more epistemic, more instrumental, I do get the impression that they crossed the line in later debates. But it’s the instrumental version that I think remains useful.
“Do you think their position holds that all of these worlds actually exist? As in ontologically exist?”
It depends on which ones you talk to. Some are agnostic about whether the other wave function branches continue to exist. Others feel they don’t. But the most vocal proponents tend to think they do exist.
As I mentioned to Wyrd, it’s an old trick in physics to introduce something but then say, “Don’t panic, this is just a useful accounting gimmick. It’s not like this crazy thing is real or anything.” This has been particularly true for quantum mechanics. Max Planck originally introduced quanta purely to make his calculations work. I suspect some Everettians take this tack to side step the ontological debates. The thing is, many things that are mathematically convenient go on to become ontological necessity.
“Reality is reality regardless of the human’s various idiotic notions.”
That may be true, but how do we know whether we know reality? I think the only answer is whether our predictions are accurate. Of course, QM can’t predict a single quantum event, only the probabilities of certain outcomes. But as the numbers of events climb, those probabilities average out to solid predictions.
“But to the extent that causality fails, as in ontological interpretations of the uncertainty associated with Heisenberg’s principle, things should not exist to figure out anyway.”
Given the above, whatever QM is, it has to be isomorphic with the reality in some way, otherwise those predictions would fail. As Wyrd mentioned, this may only be in the sense that epicycles were useful in Ptolemaic cosmology. (Interestingly, epicycles today remain as a useful perspective observational concept, despite the fact that we know they’re an illusion.)
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Mike,
If it’s the case that Bohr and Heisenberg began with a responsible epistemological position for their Copenhagen Interpretation, then why would they escalate it to ontology? Might I suggest a bit of jealousy? Even then Einstein was “the great one”. How wonderful it would feel to up him! But perhaps Einstein should mainly be blamed for selfishly not realizing that a responsible epistemological position had actually been presented, and so he chose to interprete their interpretation ontologically? Notice that “God doesn’t play dice” is an ontological claim. If he used this to counter the CI then he effectively should have goaded them into an irresponsible ontological position. And apparently they not only accepted, but used it to kick his ass! Today in popular media, and even among physicists, it’s thought that Einstein really blew it regarding QM.
I account for this incidence through a far larger structural problem. Notice that we’re asking physicists to do physics, though without provide them with any effective rules of metaphysics or epistemology to work from. Thus we should need a community of professionals armed with generally accepted rules from which to guide the function of science. Notice that the field of philosophy today has the flavor of “art and culture” rather than “science” to it. I’m not saying that this needs to change however. I’m saying that a new community of professionals must emerge that has a single mission — to straighten out science by means of its own accepted principles of metaphysics, epistemology, and axiology.
And what specifically do I propose to fix this particular mess? I’d mandate that the authors of any given position clearly state whether their proposal is theorized to just be “useful” (epistemology), or to also be “real” (ontology). Then as for those ambitions theorists that insist upon proposing an ontology regarding QM, there would be my single principle of metaphysics to contend with. Theorizing that any given bit of reality is not causally determined to occur exactly as it does occur, takes the theorist beyond the bounds of naturalism. Here there can be nothing to explain because without causal dynamics, no explanation will thus exist. This is the realm of magic. And I’m not saying that this doesn’t effectively occur. I’m saying that the position of Einstein and I, conversely, happens to be “natural”.
Well yes today, though once we have a community of professionals that’s able to effectively regulate the function of science through proven principles, there should only be “epistemic necessity”.
The only reality that I “know” exists, is that I exist in some form or other. If you’re conscious then you could say the same about yourself. And I consider it quite special to be able to truly know even that. Conversely my computer shouldn’t know that it exists (if it does exist), let along anything else.
I consider quantum mechanics to mark an incredible human achievement, though epistemologically rather than ontologically. And I do believe that it’s isomorphic with reality. But if any associated dynamic is not causally determined to occur exactly as it does occur, or “ontological uncertainty”, then the theory should effectively describe the function of magic.
But wait a minute, as I define it no explanation can exist to describe non-causal function, or magic. Right… So the effectiveness of QM theory suggests that all associated dynamics must be causally determined to occur exactly as they do occur. You’re not going to like that bit of circularity! I’ll remind you however that we’re measuring particles and waves here, though apparently matter functions as something associated but different.
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Eric,
I don’t know if you remember, but I actually think the distinction between instrumentalism and scientific-realism is a false dichotomy. We never have access to reality. We only ever have theories, predictive models about that reality. The “real” is only another more primally felt model. In the end, all we have are the models.
(This actually includes our model of self, as counter-intuitive as that sounds. Psychology has shown that access to our own mind is subject to just as many limitations as the information we get from the outside world.)
The only real distinction is between predictions that are testable and those that aren’t. The ones that are testable, and which have been demonstrated to have some level of accuracy, are “right” to whatever level they meet. But predictions that haven’t or can’t be tested should be regarded as speculative to varying degrees.
An untested or untestable prediction which is tightly bound to a tested prediction has a higher chance of eventually being shown to be accurate. But the more steps beyond observation to get to the prediction, the shakier the ground it rests on.
Under this guideline, the successfully tested predictions we have are the evolution of the wave function according to the Schrodinger equation, until information about it leaks into the environment, then we have the more definite state (position of the particle), etc. This is the instrumental Copenhagen Interpretation.
Everything else: assertions that the Copenhagen Interpretation is the only reality, pilot waves, spreading superpositions continuing under the Schrodinger equation, etc, have to be viewed as speculation, at least until someone can figure out some way to test them.
Still, speculation is fun, and should be fine as long as we acknowledge what we’re doing.
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Mike,
Well it sounds like we’re generally on the same page with that, though I wouldn’t refer to the distinction between instrumentalism and scientific–realism as a false dichotomy. Even if science only ever has models, we of course need words such as “real” which reference what actually exists beyond our models. And if some of these MWI’ers have decided that the lack of certainty in our measurements mandate “many worlds” in truth rather than simply as an accounting heuristic, then this would seem to be a wonderful example of “scientific realism”. This also strikes me as “the tail wagging the dog”.
Furthermore I don’t mind going ontological myself in some ways. I happen to believe that “God doesn’t throw dice”, which is to say I believe in absolute causality regardless of what we humans are able to figure out. Perhaps a reasonable name for this position would be “extreme naturalist”? So then what shall a person be called who makes the ontological claim that some things under a QM framework aren’t causality determined to occur exactly as they do occur? “Super-naturalist” seems over the top, and even quasi-naturalist”. So I’ll just go with straight “naturalist”, but in addition note that from this distinction “spooky stuff” does ontologically occur in some capacity.
Then there is my logical proposition from last time. My metaphysics holds that if something functions without causality, then nothing exists here to even theoretically figure out. Why? Because it’s the causality that would found any ontological explanation for any given event. The causality would be the vital element regardless of any potential understanding — nothing would otherwise exist to even look for.
I’m fine with how the QM probability distribution produces a macroscopic world which seems to function causally. But how can it be possible for something that is not perfectly caused to do whatever it does, to in the end become a causal constituent for a causal realm? I see that as a contradiction. Non-causal function, where by definition nothing exists to potentially figure out, should have no potential to produce causal function. (I suspect that there’s a simple way for this to be illustrated mathematically.) Thus if we notice that quantum function does produce causal function, then from here it must only be possible that all elements of quantum function occur causally in the end, and even if things continue to seem random to us humans.
Yes speculation is fun! Furthermore once science has better rules from which to work, it should also become more productive than today. (I see you’ve now put up a post on Sean Carrol. Sweet!)
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Eric, causality can arise from non-causal events provided that the number of events is sufficiently large. It’s the Law of Large Numbers, from probability theory.
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Interesting observation Steve! I’ve noticed a couple of interpretations for the Law of Large Numbers. One is that with enough trials, all sorts of implausible things eventually occur. The other seems more relevant however. It’s that the more times that you run a given experiment, the more statistically verified a given result will be. It’s essentially that all of these “random” results end up building a stronger and stronger case for a given figure. Is that what you meant?
I can see how it seems appropriate to apply this principle to quantum mechanics given that we’re discussing probability distributions for matter rather than exact states of being. But then again, my sense is that the LLN was set up to address every day causal events rather than quantum events that are theorized to not function causally. Does it address quantum strangeness as well? Have you found an infinitely better challenge to Einstein than the utterly pathetic “Don’t tell God what to do”? Is this a true answer, as in “God’s dice create order”? This deserves some academic consideration!
I’d be surprised if something fully beyond causality in an ontological sense is able to then go on to construct the causal function observed in nature. Causality is kind of my thing. But I’d love for this theory to get out there as a challenge to us causalists.
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While it’s true that a large number of random events will yield some rare outliers as part of the ensemble, when taken as a whole, it leads to highly predictable results. It’s the basis of statistical mechanics. Even in classical statistical mechanics, individual particles are assumed to behave randomly, but when the ensemble contains 10^23 particles, the values of pressure, temperature, etc are entirely deterministic. My statistical mechanics lecturer at university joked that when very large numbers are involved, “it is better to gamble than to count.”
Causality may be an illusion, as well as ontological fact.
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I prefer “emergent” to “illusion”, but it’s the same concept. Causality may not be the fundamental thing we take it to be.
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I agree entirely with your former professor’s observations Steve, and indeed, the Law of Large Numbers as I believe it’s traditionally been used. This is to say that if you do a single experiment a large number of times, it will continue to validate the same point in the end. And I also agree with that other interpretation. Even though a psychic may get a given prediction right, the LLN shall demonstrate the truth or falsity of this person’s powers over time.
And why does the LLN remain solid? Because of causality itself. Without an ordered world where cause leads to associated effect and the converse, it might be that the exact same experiment would not generally continue to provide the same sort of result. Or it might be that a human could indeed gain psychic powers and all sorts of “spooky” stuff. Causal order is required in order for the LLN to remain valid. Otherwise we’d need to count rather than to gamble.
I suppose that this is why advocates of ontological voids in causality haven’t yet tried to use the LLN to argue their case. Thus we instead get pedigreed snake oil carnival hawkers like Sean Carrol. Apparently people love hearing this sort of thing.
(I haven’t yet found a mathematical proof that causality can’t emerge from non-causality, but perhaps I will.)
Mike,
If it’s true that there is a fundamental uncertainty to QM function, then yes, the causality that we observe must emerge from non-causality. Or it could be that there is a causality which we don’t grasp here given that we erroneously perceive existence in terms of particles and waves.
Right. But a better way to say this might be that causality may or may not be absolute. Somehow to me your statement implies that we’d still call something “causal” even if it isn’t. Or perhaps I’m being pedantic? You wouldn’t term something “causal” if it weren’t causally mandated to occur in the exact manner that it does would you?
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Eric,
If causality is emergent, that is, real but a composite process made up of lower level processes which are not themselves causal, then I would use it in the same manner I use “temperature”, “weather”, or “molecule”. Each of these things objectively exist, but are composed of things which are not that thing, in other words, they are composite phenomena.
The idea that causality is a composite phenomena is very counter-intuitive, but then so are many things in science.
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All true Mike, so apparently I was being pedantic there. If causality emerges from non-causality then it isn’t the fundamental thing that we take it for, similar to “molecule” and all the rest. But given our flawed perspectives I do still suspect that it’s fundamental in the end.
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Great post, and a clear summary of the position. I (like most people) have problems with all the proposed solutions, and that is as it should be, since none of them are entirely persuasive. The most unconvincing commentators are those who argue passionately for one particular interpretation.
My gut feeling is that we are still missing a fundamental insight, and I hope this will emerge either through some new observation, or else a new theory. My instinct is that entanglement holds the key to unlocking the answer. Disclaimer – it may be that this is wrong, and that it is just me who is lacking the fundamental insight 🙂
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Thanks Steve!
In recent decades, decoherence has become the preferred description of what happens when the wave appears to become a particle. Under that description, what actually happens is the wave becomes “entangled” with the environment. So your gut may be on to something!
It feels like all physicists can keep doing is testing the boundaries of this stuff until something unexpected comes up. After all, it was the necessity of dealing with bizarre observations that initially forced them to their current understanding of QM, such as it is. The answer probably lies in continuing to pile up those observations until something new emerges from the data, but that might take decades or centuries.
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I hadn’t heard of the spreading superposition idea before. I can’t give much of an opinion about that except to say that it’s a really cool idea.
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The phrase “spreading superposition” is one I use to communicate the core proposition of the Many Worlds Interpretation. There’s probably a more technical term out there.
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