[millstone]

No offense intended, but the "lost contact with empirical reality" critique really lands for the above description of MWI. A mathematical construct (the wavefunction) is taken as more real than basic empirical experiences like "measurements" and "we."

[adeledeweylopez]

One of the major aims of physics is to try to describe reality with mathematical constructs.

If you start with what can be directly observed or experienced, then that's phenomenology.

Those are both valid and interesting ways of trying to understand reality, and I believe they are ultimately fully compatible with each other. But I think you are trying to hold physics to phenomenology standards in a way that doesn't make sense. No one thinks that Newton's theory of gravity "lost contact with empirical reality" because it doesn't have measurements or people as ontological components.

Anyway, that's all beside the point I was trying to make, which was just that the description of the MWI in the article was plain wrong.

[Ma8ee]

But Newtonian physics is compatible with our experience of reality. The Many Worlds Interpretation as described above isn’t.

[Extigy]

Not necessarily. When you live inside the wavefunction the outcomes of certain experiments very much look like a wavefunction collapse. MWI is a way to explain why that happens without having to have a special case where the universe has a completely different behaviour for just a moment in time.

You can formalise the mathematics of it using the concept of quantum decoherence.

[DiogenesKynikos]

How is MWI incompatible with our experience of reality?

[TheOtherHobbes]

We experience one reality, not many realities.

MWI handwaves that problem away without really explaining it. "It's random but subject to the Born Rule" is a description of what's already observed, not an explanation with predictive power for new and distinct observations.

There are much more complex criticisms that use words like "ontic" and "epistemic", but that's the fundamental problem that MWI claims to solve but doesn't.

[DiogenesKynikos]

> We experience one reality, not many realities.

How does MWI imply that we should simultaneously experience multiple realities? If two different states of you experience two different realities, each state of you is only aware of one reality.

MWI largely reduces to something like the Copenhagen interpretation for large systems. It's just that MWI explains the transition between the quantum and classical regime, doesn't require any ad hoc rules about observers, and doesn't need Schrödinger's equation to be violated.

[MacsHeadroom]

The claim wasn't that we should experience inaccessible worlds for MWI to be compatible with our experience of reality. That's obviously absurd.

The claim was that inaccessible worlds are inherently incompatible with our ability to empirically investigate or falsify them (via experience).

MWI has a metaphysical parsimony to it. But to believe it's physics is religious faith not physical science- and that's fine, but it's still not science.

I don't think collapse is real either. I think it's a phenomenological byproduct of consciousness requiring particilarity to model the world it perceives. You've already alluded to that being the case ('we can only experience our worldline').

If you knew the metaphysics behind that particularity well enough, you'd also know that it leaves no ground for and has no need of the existence of a physical material reality to begin with. As such, materialist physics has already made an epistemic leap which inevitably leads to mistaken intuitions about the most reasonable ways to interpret empirical phenomena.

[jungturk]

> We experience one reality, not many realities.

Isn't that just a claim about the sensitivity of the detector?

I'm sure folks were dubious about the theory of the electromagnetic spectrum given their bias to visible light, but as experiments improved and detectors with them it doesn't seem so farcical.

[meroes]

It's not though. Instantaneous gravity, third law, etc, are not true in GR.

[cjfd]

From a physics point of view this is a very strange thing to say. Why are 'we' or 'measurements' things of special status? Because we have a soul or something? Now, that would be a theory where an abstract concept is taken to be more real than observable things. The measurement apparatus is also a physical thing that should be described by the physical theory in use as would the humans be. The very painful point about the copenhagen interpretation is this distinction between 'normal' time evolution and the special procedure when a 'measurement' is carried out. Actually, there exist mathematical proofs that the normal time evolution when applied in cases where information is transferred from microscopic stats to macroscopic ones leads to something that looks like a collapse of the wave function but is actually a split of it. This is as a physical theory much more attractive than giving a 'measurement' a special status. The question what this all means is a bit more mind-boggling though including multiple worlds and that kind of stuff. Taking 'a mathematical construct as more real than basic empirical experiences' is basically the history of physics and it has in the past been highly successful.

[chongli]

Why are 'we' or 'measurements' things of special status?

Because we experience the world through our senses. Everything else is one mathematical model or another that we’ve created. And our models aren’t even consistent!

very painful point about the copenhagen interpretation is this distinction between 'normal' time evolution and the special procedure when a 'measurement' is carried out

This is not a special procedure. Measurement occurs whenever physical interactions take place. To measure a particle, we bounce another particle off of it and then try to detect the result. The measurement is the particle collision, not the detection. It’s like playing billiards in the dark. We don’t know where the balls are.

Taking 'a mathematical construct as more real than basic empirical experiences' is basically the history of physics and it has in the past been highly successful.

Except for all of the times when it broke down. When one model was found to contradict our experiments and we had to replace it with another, which later turned out to be wrong as well. Perhaps the most embarrassing example of this, in human history, is all of our attempts to make geocentric models work [1].

The most well-known critique of science’s institutional habit of inventing new models whenever old ones broke down is probably Kuhn’s paradigms [2]. If you’re interested, you’re better off reading Kuhn than anything I have to write here. I think the best evidence for Kuhn’s thesis is the abject disappointment we witness every time particle physicists fail to overturn the standard model. If that’s not supremacy of measurement, then I don’t what is.

[1] https://en.wikipedia.org/wiki/Geocentric_model

[2] https://en.wikipedia.org/wiki/The_Structure_of_Scientific_Re...

[pontus]

You say "The measurement is the particle collision, not the detection.", but this is not right.

When two particles bounce off each other, there is no collapse according to traditional copenhagen, instead the wave function just evolves according to the SE. Even worse, when that particle (let's say photon) then travels to the measurement device to interact with the particles that make up that machine, the evolution is similarly governed by the SE. Somehow though at some point, nature decides that a measurement has taken place and collapses the wave function. What dictates where that happens? Honestly this way of thinking about it makes no sense to me. The MWI is, to my mind, the simplest explanation for all of this mayhem.

[crdrost]

I do not believe they are arguing for a soul but rather just pragmatism. It's not that “measurement” has some special status as coming from a soul or something: indeed your unwillingness to see it as a normal thing that happens, such that you immediately jump to this question, indicates that you have already “drunk the Kool-Aid.”

This is more clear in Everett's original formulation. Everett didn't speak of “many worlds” but of a difference between relative and absolute truth. You measure a spin-½ particle along some axis, it is only “relatively” true that you saw what you saw, say ↑, and there is also a relative truth that you saw ↓. But because these relative truths are exhaustive there is also an absolute truth that you have the deluded belief that you saw either one or the other; that truth holds in both relative truths. The “lost contact” objection is precisely that in Everett's theory this belief is ultimately delusional (there is nothing like collapse to which they correspond, it is just formally incorrect to confuse your relative truths with the absolute truths) and we are led by the theory to delusions like this “with high probability” (scare quotes because Everett realized more so than his successors that eliminating collapse also untethers the theory from probability in a deep way). It is just accepted that these deeply practical things like “my existence as an observer” and “my tool’s measurements” are ultimately based on a sort of illusion which has no correspondence to the true reality; this is buried in a mathematical technicality in his thesis (he notes that he is not looking for an “isomorphism” between experience and the external world, but a “homomorphism”), but it is kind of the crux of the whole enterprise. “It’s fine if I predict things which are not observed, so long as I also predict the things that are observed and I predict that you will be very opinionated about not observing the things predicted but not observed,” if you will, is the homomorphic approach to QM that Everett advocates.

In that respect there is something very different from “the history of physics.” Physics does in some cases say that certain things are illusions. And those statements track very closely with MWI. For example a rainbow appears to be a thing out in the world, but modern physics is very happy to say that the phenomenon cannot be correctly located as an object inside the cloud in which it is perceived, because it turns out the cloud is “rainbowing” in different ways in many different directions and you are only getting part of the story. You see part of the light suggesting a reconstruction of a physical object, but if we look at all of the light we realize that the different reconstructions are not reconcilable because they all have to occur at a 41° angle from the rays of the Sun and real objects have varying angles.

You can see a lot of similar ground trod here. Both claims of illusion appeal to the act of trying to reconstruct the external world from observed experience. Both then appeal to looking at all observations taken together. But there is a difference in scope. In the rainbow case there is a counterfactual, a “what you would have seen,” that can be confirmed with a camera at some other location. We can do a parallax measurement to reconstruct that the rainbow is actually around as far away from you as the Earth is from the Sun or so. But in MWI these sorts of experiments which may be possible are ultimately forever infeasible, I need to have quantum control of every atom of my measurement apparatus if I want to make some similar observation, and even then any particular observation will be consistent with a classical ontology, it's just the pattern of many observations which will suggest non-local correlations which I can interpret as evidence for maybe everything being illusory. One rocks your boat gently, the other is sailing in a hurricane.

[feanaro]

I think there is some misunderstanding here based on the wording used. OPs point is simply that there is no separate, explicit branching process. Instead, there is only the normal, continuous evolution of the wavefunction.

Our experience is recovered from this by positing that subjective/phenomenological experience is somehow tied to the individual components of the wavefunction. Since the individual components don't interact with each other, it gives the appearance of branching. This is compatible with our observations.

[ithkuil]

Furthermore it firmly places ourselves and our own experiences within the very same fabric of reality it's describing. This is a rather inevitable problem of a fundamental theory of reality, since we ourselves are part of it and our inner working (whatever that is) must be layered on top of that fundamental machinery.

[kgwgk]

So we get from the “the wave function somehow collapses” to “the phenomelogical experience is somehow tied to the individual components wave function” which are somehow connected go the measurements.

[feanaro]

You're right regarding the first part, we don't have a clear explanation of how the wave function might be related to subjective experience, but that's mostly because we don't have a good account of subjective experience at all.

For the second part, there's nothing mysterious going on at all: measurement is simply physical interaction.

[kgwgk]

What are "the individual components of the wave function"? They are a mathematical construction. The wave function can be decomposed in many (and infinity of) ways. Why is one decomposition chosen and not another? Or are all the decompositions equally "(un)real"? The issue is not so simple and it's related to the "mysteriousness" of the first part.

[Konohamaru]

How do we know that opponents of MWI aren't succumbing to antibrunoist prejudice?

> [Giordano Bruno] is known for his cosmological theories, which conceptually extended the then-novel Copernican model. He proposed that the stars were distant suns surrounded by their own planets, and he raised the possibility that these planets might foster life of their own, a philosophical position known as cosmic pluralism.

I need to point out that he was burned at the stake for advocating cosmic pluralism.

[canjobear]

Later observations proved Bruno's speculations to be correct.

But MWI does not make different predictions from other quantum interpretations. No observations can confirm or falsify it.

[baddox]

Modern cosmology by definition doesn’t make different predictions than saying “cosmological models mention things like stars and galaxies, and those models fit our observations, but those stars and galaxies aren’t technically real.”

[Konohamaru]

Maybe in the greater context of our universe cosmic pluralism is a design pattern, which would make MWI a more preferred interpretation.

[phaemon]

> I need to point out that he was burned at the stake for advocating cosmic pluralism

I need to point out that he wasn't. His heresy trial had nothing to do with his cosmic beliefs. He was convicted for teaching religious beliefs, as a Catholic, that were contrary to Catholic dogma. The church punishment for this was excommunication but the secular punishment was execution, so he got burned.

[Viliam1234]

> A mathematical construct (the wavefunction) is taken as more real than basic empirical experiences like "measurements" and "we."

In chemistry, atoms are also taken as more real than "measurements" and "we". Some chemists would probably insist that "we" are actually composed of atoms.

[baddox]

The mathematical construct was developed/discovered to explain observations. Normally when we do that we consider the mathematical explanation to be “real” in that it is describing reality.

[sullyj3]

I mean, it seems strange to reject implications of a successful model if those implications aren't observable. Eg, I believe that stuff exists outside our light cone, because it would be unparsimonious for there to be an extra rule saying that stuff that I can't access doesn't exists.