I’m reluctant to engage with extraordinarily contrived scenarios in which magical 2nd-law-of-thermodynamics-violating contraptions cause “branches” to interfere.
Agreed. Roland Omnes tries to calculate how big the measurement apparatus of Wigner needs to be in order to measure his friend and gets 10 to the power of 10E18 degrees of freedom (“The Interpretation of Quantum Mechanics”, section 7.8).
But if we are going to engage with those scenarios anyway, then we should never have referred to them as “branches” in the first place, …
Well, that’s one of the problems of the MWI: how do we know when we should speak of branches? Decoherence works very well for all practical purposes but it is a continuous process so there isn’t a point in time where a single branch actually splits into two. How can we claim ontology here?
Thanks, I see we already had a similar argument in the past.
I think there’s a bit of motte and bailey going on with the MWI. The controversy and philosophical questions are about multiple branches / worlds / versions of persons being ontological units. When we try to make things rigorous, only the wave function of the universe remains as a coherent ontological concept. But if we don’t have a clear way from the latter to the former, we can’t really say clear things about the parts which are philosophically interesting.
So much the worse for the controversy and philosophical questions. If anything, the name is the problem. People get wrong ideas from it, and so I prefer to talk in terms of decoherence rather than “many worlds”. There’s only one world, it’s just more complex than it appears and decoherence gives part of an explanation for why it appears simpler than it is.
Unfortunately, what I would call the bailey is quite common on Lesswrong. It doesn’t take much digging to find quotes like this in the Sequences and beyond:
This is a shocking notion; it implies that all our twins in the other worlds— all the different versions of ourselves that are constantly split off, [...]
Agreed. Roland Omnes tries to calculate how big the measurement apparatus of Wigner needs to be in order to measure his friend and gets 10 to the power of 10E18 degrees of freedom (“The Interpretation of Quantum Mechanics”, section 7.8).
Well, that’s one of the problems of the MWI: how do we know when we should speak of branches? Decoherence works very well for all practical purposes but it is a continuous process so there isn’t a point in time where a single branch actually splits into two. How can we claim ontology here?
I don’t think it’s a problem—see discussion here & maybe also this one.
Thanks, I see we already had a similar argument in the past.
I think there’s a bit of motte and bailey going on with the MWI. The controversy and philosophical questions are about multiple branches / worlds / versions of persons being ontological units. When we try to make things rigorous, only the wave function of the universe remains as a coherent ontological concept. But if we don’t have a clear way from the latter to the former, we can’t really say clear things about the parts which are philosophically interesting.
So much the worse for the controversy and philosophical questions. If anything, the name is the problem. People get wrong ideas from it, and so I prefer to talk in terms of decoherence rather than “many worlds”. There’s only one world, it’s just more complex than it appears and decoherence gives part of an explanation for why it appears simpler than it is.
Unfortunately, what I would call the bailey is quite common on Lesswrong. It doesn’t take much digging to find quotes like this in the Sequences and beyond: