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.
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.
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.
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.
That's not what the claim was. The original claim was that MWI is "incompatible with our experience of reality." TheOtherHobbes then said that the incompatibility is that we experience only one reality, instead of many realities.
> 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.
It's not religion to point out that QM explains the phenomenon of wavefunction collapse without any additional postulates (through decoherence). That's all that MWI says.
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.
You can formalise the mathematics of it using the concept of quantum decoherence.
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...
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.
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.
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.
For the second part, there's nothing mysterious going on at all: measurement is simply physical interaction.
> [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.
But MWI does not make different predictions from other quantum interpretations. No observations can confirm or falsify it.
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.
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.