The MWI is a simpler theory than other interpretations because it does not require "collapse" to be a physical process. The "realness" of the other worlds is untestable, but also not part of the theory.
"unreal" MWI should be the null hypothesis given what we know to be true about quantum mechanics. If we find evidence that collapse is a physical process then we can reject it, but otherwise it makes the fewest leaps. At the moment the Copenhagen intepretation is taught instead, which is a problem. To quote wikipedia:
> There is no uniquely definitive statement of the Copenhagen interpretation
And
> the device used to observe a system must be described in classical language, while the system under observation is treated in quantum terms
In other words, it does allow you to predict the result of an experiment, but we know it can't be right because it's impossible to formalize without building this "classical observer" into the model. Attempting to build on this inevitably leads to metaphysical nonsense about consciousness.
In "unreal" MWI there is a universal wave function, and something is "real" to us if it is entangled with us. The "many worlds" terminology makes it easier to visualize but doesn't mean those other worlds are real because whether something is real is subjective in this interpretation. Subjective reality may be a problem for some people, but if you look at the evolution of physical theories, we consistently find that everything is more subjective than we thought it was (see also: relativity).
Believers in Everett may not end up being right. But believers in Copenhagen aren't more right than believers in Everett. In fact, they "aren't even wrong" either, because they refuse to even engage with the question. So I think it's like the situation with democracy. You have to go with Everett until you find something better, providing you want to be scientific at all.
The MWI is a simpler theory than other interpretations because it does not require "collapse" to be a physical process. The "realness" of the other worlds is untestable, but also not part of the theory.
"unreal" MWI should be the null hypothesis given what we know to be true about quantum mechanics. If we find evidence that collapse is a physical process then we can reject it, but otherwise it makes the fewest leaps. At the moment the Copenhagen intepretation is taught instead, which is a problem. To quote wikipedia:
> There is no uniquely definitive statement of the Copenhagen interpretation
And
> the device used to observe a system must be described in classical language, while the system under observation is treated in quantum terms
In other words, it does allow you to predict the result of an experiment, but we know it can't be right because it's impossible to formalize without building this "classical observer" into the model. Attempting to build on this inevitably leads to metaphysical nonsense about consciousness.
In "unreal" MWI there is a universal wave function, and something is "real" to us if it is entangled with us. The "many worlds" terminology makes it easier to visualize but doesn't mean those other worlds are real because whether something is real is subjective in this interpretation. Subjective reality may be a problem for some people, but if you look at the evolution of physical theories, we consistently find that everything is more subjective than we thought it was (see also: relativity).