Schrödinger's Dog said:
I still can't help thinking though that MWI is making an assumption based on assumption. Using Occam's razor I would say it's too complex and invoking properties that it need not, my personal view is that we're not quite their yet, we haven't quite got how it works, so therefore anything based on the extension of what we know at the moment is subject to being based on faulty suppositions to begin with.
We will ALWAYS be in that case, as long as we (and our descendants, or another species which thinks about physics) will be around. We will always have a finite knowledge, and we will always have to "extrapolate" if we are going to pose grand visions of the meaning of life, the universe and everything. So "waiting until we finally find out" is Waiting for Godot.
My point is simply this: *IF* we insist on having a world picture, then it seems more reasonable to do this by extrapolating currently well-established theories than to postulate half-baked and not-yet-completely-worked-out dreams of theories of what "ought" to be (
this sounds like string theory
). So, totally aware of the extrapolation and its hypothetical character, I think it is more conservative to stick to the principles of established theories than to invent properties of principles of unestablished theories, and it is based upon that attitude that I think that an MWI view is more natural with quantum theory than a Copenhagen based view. But I'm well aware of the extrapolation this contains. I would even say (with Penrose), that there is probably a serious problem, which is gravity. But, or unitary quantum theory can cope with gravity (in which case the serious problem disappears), or unitary quantum theory will undergo a modification in order to deal with gravity, in which case we will not need an interpretation of unitary quantum theory anymore (and maybe we can do away with MWI, depending on how the new, and unknown, theory will be put together). However, given that at this moment, the only thing we have, is unitary quantum theory, we extrapolate to its universal applicability, and then you end up with MWI in one way or another.
In this light, MWI is rather favored by Occam's rasor. Because what is "cut away" is all the extra hypotheses needed for the NON-applicability of unitary quantum theory (somehow the EXTRA rules that say that the superposition principle is NOT applicable to humans or so).
There are two ways to consider Occam: one can try to simplify the RULES of the game (that is, cut away all extra rules which don't bring in anything), or one can cut in the acceptable solutions: that is, by adding rules, we can limit the kind of solutions we like to see. Usually, with Occam's razor, one means the first kind of simplification: one likes to limit the number of RULES, and wants to apply them as universally as possible. If this leads to a more involved set of solutions, then so be it. In this light, applying the superposition principle universally is a simpler view (preferred by Occam) than specifying extra rules of when it applies, and when not, and what to do when not (projection).
Now, I can accept very well that people "shut up and calculate", because strictly speaking, that's what science is about: building models which make predictions and falsify them. It is when people start to talk about the weirdness of quantum theory (and more specifically about its confrontation with logic, or its lack of sensibility or the like) that I like to bring up an MWI view. In those "paradoxial" situations, like EPR-Bell, or delayed quantum erasers and so on, this view really helps "understanding" the quantum-mechanical machinery (in the same way as imagining that a spacetime manifold is curved helps you understand general relativity), and avoids all these "impossibilities" which are displayed. But if you are happy with saying "hey, that's what comes out of the calculation, and that's also what we find experimentally", then that's also fine. It is when one starts saying "uh, this must be wrong, this doesn't make any sense, although we calculate it, and we measure it all the same", that it helps to consider exactly what we assumed as a starting point and how these very same assumptions are also the key to the "understanding" of the "paradox".
Not that I think QM is wrong, I haven't seen anything that would suggest that, just that when you read a discussion about what a wave function describes, you tend to get the impression that it's pretty much a matter of mathematical interpritation, and obviously that's because we cannot observe directly a superposition.
Well, it is part of the superposition principle that we can't observe it directly ! However, we can observe its consequences indirectly (each time this happens, we talk about a "quantum effect" or something of the kind).
Sometimes when I'm floating around discussions, I often have to ask myself, how do you make that out? I could as easilly say x a lot, it's all a little to grey to start making hypothesis based in incomplete theory, in other words let's get the foundation right first before we start invoking strings and many worlds.
We will never be sure that we have the foundations "right", and we will always have an "incomplete theory". There may be moments when we will be deluded in thinking that we have it all right. Happily right now that's not the case: we KNOW we don't know everything. The day we think we do, we are deluding ourselves.
Again, MWI is just a conceptual tool to help you understand quantum theory, as we have it right now, in the same way as the spacetime manifold is a tool to understand general relativity, or Euclidean space is a tool to understand our visual impressions.
There is no reason to assume God exists, their is no reason to assume he doesn't scientifically either. But logic and proof are very different beasts.
True, but there's a difference. It is a common misunderstanding of MWI that one has *introduced* the idea of "several worlds". As I tried to point out: this is a *consequence* of applying a basic postulate strictly and universally. If we used a theory in which there was a fundamental postulate that introduced a deity for the behavior of electrons in an atom, then wouldn't it be natural to assume that that deity also existed for us ?
THIS is what is done in MWI: we APPLY an *already existing postulate* of the theory universally, beyond where it is "really needed". We don't introduce a totally new concept (such as a deity). It also indicates the weakness of an MWI view: it might be that the postulate is *not* universally true, and then of course, the view based upon it doesn't make any sense. But that day, we will also know WHAT is then applicable. Up to today, we haven't gotten any indication of a limitation to the applicability of the superposition principle (but gravity might be a spoiler - we simply don't know). As such, we can only GUESS at what might eventually replace it, IF it even needs replacement. So all non-MWI views are in fact based upon a *guess* of new physics - usually to bring it in agreement with intuitively more acceptable macroviews.
And WHEN we do so, we run into a lot of paradoxes. So why do this ? Clearly, the day that we DO KNOW whether or not the superposition principle has limitations of its applicability, and we DO KNOW what replaces it eventually, we will also know what are the solutions to eventual "paradoxes". So we shouldn't worry about that. But right now we don't. So let us not worry about paradoxes that might not even be there, and which aren't there when we extrapolate our current theory's principles.
Thanks. That's indeed EXACTLY what I wanted to say. But I didn't, you did