I think there was also a concept for scientifically testing the MWI, but that only works subjectively. You essentially play Russian roulette, preferably based on the outcomes of a quantum measurement. Repeat until you either die or are satisfied that the world you are in is so implausible as to be impossible unless indeed every outcome is realised.
Say, fire an electron at a double slit with a detector in one of the slits, and kill yourself if the particle is not detected. Run the experiment 10,000 times, or 100,000,000 times - one copy of you will eventually be satisfied that in any probabilistic interpretation of QM this is not plausible, and all the other copies will be dead.
This works because the MWI predicts that any outcome that has non-0 probability according to the Born rule will be guaranteed to happen (it just "happens less" by some hard to define metric).
Personally I believe the entire notion is absurd, and that this type of thought experiment makes it clear, but still some like to be contrary.
Say, fire an electron at a double slit with a detector in one of the slits, and kill yourself if the particle is not detected. Run the experiment 10,000 times, or 100,000,000 times - one copy of you will eventually be satisfied that in any probabilistic interpretation of QM this is not plausible, and all the other copies will be dead.
This works because the MWI predicts that any outcome that has non-0 probability according to the Born rule will be guaranteed to happen (it just "happens less" by some hard to define metric).
Personally I believe the entire notion is absurd, and that this type of thought experiment makes it clear, but still some like to be contrary.