Hurd has always seemed cool from the purist viewpoint of, "Let's prove to the world that we can do everything using a microkernel!"-- and to be frank, as a Haskell lover, it would be hypocritical for me to fault anyone for this level of purity!--but development has been plodding along for decades, with the article claiming (unless I misread it) that they are still working on things like SMP and 64-bit support.
I mean, as long as the people tinkering with this are having fun then that is all that really matters, and more power to them! However, that really seems to be the entirety of its purpose at this point, which is a shame given the lofty ambitions with which the project was launched.
I think to some extent we have been talking past each other. Very roughly speaking, I think that am more worried about what happens in the middle of an experiment, where you are more worried about what happens at the end. I actually completely agree with you that when a conscious being performs a measurement, then, from the perspective of that being, both interpretations of what happened when it performed the observation are equivalent. That is, the being has no way of telling them apart, and asking which interpretation is true at that point is, in my opinion, roughly along the same lines as asking whether the objective world exists.
(Just to be clear, it's not my intent to get mystical here. I think of consciousness as essentially just being a way of processing information about the world, rather than positing the existence of souls.)
The analogy to Galilean relativity actually is too kind. Galilean relativity relies on Euclidean space as a background, allowing an external viewpoint fixed to empty coordinates. Hilbert space is not a background space at all; it is always defined in terms of physical systems, what is known as a constructed space. You can transform perspectives in spacetime, but there is no transformation to a background perspective in Hilbert space because no such background exists. The closest that exists is a statistical transformation to different perspectives within Liouville space, but this only works for objects within the space; you cannot transform to the perspective of the background itself as it is not a background space.
...which is why eventually you need to switch to the grown-up version of Quantum Mechanics, Quantum Field Theory, is defined in terms of relativistic fields with a single "universal" field for each flavor of particle.
I assume you have an emotional attachment to MWI without even having read Everett’s papers and getting too defensive that you refuse to engage seriously in anything I say, so I am ending this conversation here.
Uhh, okay. Like, you were the one who felt the need to go on the attack here, but if you need to stop for your mental health than so be it. 🙂
To clarify my imprecise language, what "breaks down" is not its ability to give the correct answer, but the ability of the conceptual framework to give a clear explanation of what is going on, because it essentially defines measurement as "you know one when you see one", which can lead to confusion.
(However, separately, I do feel the need to point out that "entanglement" is not at all a term that is related to measurement results per se, but rather to the state of a system before you measure it. In particular, if a system is entangled, you can (in principle) disentangle it by reversing whatever process you used to entangle it so that you no longer get correlations in the measurements.)
Again, as I said in my comment, the branches in MWI are just a visualization of the very simplest possible case, not a literal description of reality. It is unfortunate (though understandable) that people have latched on to them as if they were the central idea of MWI.
A simpler way of stating my point is that entanglement is sufficient to understand measurement, and more importantly, what phenomena are "measurement-like" and which aren't. Also, you missed my point regarding the Born rule. You can write down a mathematical model of an experimenter repeating an experiment and recording their measurements, turn the crank, and see the probabilities predicted by the Born rule fall out, without any experiment ever having taken place.
I am confused, then, about what we are supposedly even arguing about here. (Are you sure you are even arguing with me, rather than someone else?)
I did some searching and I think that what you are calling "relative states" is an older term for what we now call "entangled states". Being entangled with another system implies (by definition) that there is a greater system containing you and the other system, and so on, which is how you end up with a universal system that contains everything. However, we do not actually believe that reality is dictated by quantum mechanics but by quantum field theory, which is manifestly built on top of special relativity and posits a single field for each kind of particle for the entire Universe, and describes the microscopic behavior so well that it is absurd. Of course, the next step is figuring out how to reconcile this with general relativity, but that isn't something Copenhagen helps you out with either.
First you criticize the way that I talked about branches, which I only mentioned briefly as a sort of crude visualization and explicitly called out as being such. Now you are claiming that I am "denying the physical existence of real-world discrete outcomes"?
Yes, but it can be mathematically proven that this world was only made possible by the decimation of the population due to the tide pod challenge having been started two years earlier.
What freedom is being taken away from you, personally, exactly, that makes it so bad that they decided to go with this license?