I also think you are taking the MWI vs. Copenhagen too literally. The reason why they are called interpretations is that they don’t literally say anything about the actual underlying wave function. Perhaps, as Goofus in your earlier posts, some physicists have gotten confused and started to think of the interpretations as reality. But the idea that the wave function “collapses” only makes sense as a metaphor to help us understand its behavior. That is all that a theory that makes no predictions can be—a metaphor.
MWI and Copenhagen are different perspectives on the same process. Copenhagen looks at the past behavior of the wave function from the present, and in such cases the wave function behaves AS IF it had previously collapsed. MWI looks at the future behavior of the wave function, where it behaves AS IF it is going to branch. If you look at it that way, the simplest explanation depends on what you are describing: if you are trying to talk about YOUR past history in the wave function, you have no choice but to add in information about each individual branch that was taken from t_0 to t, but if you are talking about the future in general, it is simplest to just include ALL the possible branches.
Seriously, agreeing with Caledonian.
I remember Eliezer wrote an earlier essay to the effect that GR is a really simple theory, in some information-theoretic sense, and therefore we should optimize our theories based on their information-theoretic complexity. But what’s being missed here is that GR (and SR and Newtonian physics and arithmetic . . .) are simple stated on its own terms. That’s WHY it’s a paradigm shift. If you tried to state GR strictly as a modification of Newtonian mechanics in a global coordinate system, you would either fail, or you would end up with something incredibly complex that would appear implausible by information-theoretic counts.
The bits that you fail to count, when looking at a simple theory, are the bits required to represent the entire worldview, which don’t seem like they’re information because they’re just how you look at the world.
What you’re trying to do is find a local optimization in theory-space, but all you’re working with is a projection of theory-space onto the sub-space that is our current way of thinking, and then you find your objective function is not quite zero, but you wave your hands and say, “Hey! It’s lower than what we had before! Why did it take people 30 years to reach this not-quite-minimum when all they had to do was descend the gradient?” I think a lot of people would rather just wait around for someone to come along with an answer that really does minimize the objective function.
Somehow you have to hit upon the right projection of theory-space that happens to include all the right variables. If you have a mistress, I invite you to retire to a cottage with her for a month and see if that helps.