confusedashell said:
Either way, MWI might as well NOT be true? there is no evidence? I keep eharing about Deutsch claiming there is evidence because he has seen some **** he thinks he has seen or some ****.
For me I think his hallucinating, this guy insist on MWI so much it's like a religion for him.
I think you're more in for a basic course on philosophy (and philosophy of science) than for a course on quantum mechanics
As I tried to point out earlier, scientific theories never talk about "what's true": there is scientifically no way to know what is "true", the only thing we can say about scientific endeavour is to say that there's a theoretical model of reality that makes correct observational predictions. But that's never a proof that the theoretical model is "true" ; only, it is a practical mnemonic (as OOO pointed out) to "tell yourself" that this is how nature "really" is. A good theoretical model doesn't only make right predictions, it also comes with a "picture" of reality.
Now, one of those theoretical models which is highly successful in explaining a tantalizing amount of observations is quantum theory. The problem with this theoretical model is that no matter how you turn it, it is difficult to get a fully consistent *picture* out of it. Most of the time (from the very beginning) people have been *fiddling with the theoretical model* in order to get out a "nicer picture", but it always gives some strange quirk. MWI has the advantage of NOT fiddling with the formalism, but to keep it the way it is built upon its elementary axioms. I find this personally the most attractive part of MWI, because it fullfills its role as a "mnemonic" best. But it is true that the picture that comes out of it is indeed very strange, and can have very weird philosophical implications.
So I consider MWI indeed as the best "mnemonic" for doing quantum theory as we know it. Whether it is "really true", I haven't gotten a clue. I don't think that MWI is the best mnemonic to study romantic relationships, for instance, but usually you don't consider romantic relationships in the framework of quantum theory.
However, there's something disturbing in your phrase, where you desperately HOPE that MWI is not true, for its implications on your view on romantic relationships. But that's the most anti-scientific attitude you can have ! This kind of attitude is what breeds creationists (evolution might just as well not be true ? Gosh, I would hate it to descend from an ape, and not from Adam and Eve...) From the moment you have emotional involvement in a possible scientific statement, you're out of science.
So, I'd say, cool down. First of all, you should study some philosophy of science, and about what can be known and not. Then you should study the formalism of quantum mechanics (and probably you'll understand where the MWI idea comes from: it comes from the axiom of superposition, applied to macroscopic states). And then you should realize that MWI is just *A* picture of A current theory. I think that picture does a great job in helping one understand that theory. In my eyes, it is the most elegant view on the quantum formalism. But I'm far from sure that 1) it is the "correct" picture and 2) that this current theory will remain so for ever - especially with gravity there is some serious issue for instance. But it might be. As always, we can't know what is "really true" in science, we can only say that we have models which give good predictions in agreement with observation.
Incidentally, I don't think anything in this thread is MWI-specific; they have been philosophical issues for thousands of years.