zlacker

Many-worlds is not necessarily impossible to verify experimentally, because it predicts that there is no collapse of the wave function, whereas Copenhagen claims that there is. Many-worlds is not just an interpretation in that sense, it’s a theory that makes predictions (by reasoning about what happens when the wave function is all there is and always evolves according to the Schroedinger equation — it is a deterministic theory in that sense). I believe Einstein would have liked it, given the experimental evidence we have since.

Copenhagen, on the other hand, doesn’t offer a workable model of how and when the wave function collapses, and doesn’t offer any predictions in that way (there are theories of wave function collapse that actually make predictions — some of which have already been falsified by experiment). For that reason Copenhagen isn’t “least objectionable”.

>>layer8+(OP)
One of the key phrases I said was "(if you have to make one at all)" -- wavefunction collapse is inherently messy, since the notion of measurement is not well-defined or understood. I would argue that "don't care" is likely a more common interpretation among practicing physicists (of which I am emphatically not!), as this is very much in a realm where general intuition largely does not apply.

Copenhagen is basically an admission that we have no good intuition for why QM behaves the way it does, and wavefunction collapse is merely a way of justifying existing observations within the framework of QM.

IMO all the discussion about how wavefunction collapse doesn't scale to larger ensembles of particles, or the boundary between QM and Newtonian mechanics being ill-defined is noise -- the bridge between the two is statistical mechanics, where classical mechanics only arises from sufficiently large macrostates such that you can aggregate out any quantum mechanical properties. And QM is generally understood to be a toy model in the same way that Newtonian mechanics is a toy model -- it's useful in the realm where we use it, but when you push beyond the limits of that realm, its deficiencies become apparent.

That's why I don't think the proposed experiments to test many-worlds are particularly meaningful (since AFAIK they all seem to involve performing interference on enormous ensembles on the scale of entire humans) -- it's well beyond the limits of where QM is useful (also, I personally don't think we'll ever be able to operate quantum-mechanically at that scale).