In his 1985 paper, “Quantum theory as a universal physical theory”, Deutsch writes:

> I have pointed out several times in the preceding sections that the C.I. and the Everett “interpretations” are really different formalisms for quantum theory—in effect, different physical theories. It is usually claimed that although their assertions as to the nature of objective facts are radically different, the two “interpretations” agree about all subjective experiences of observers, and cannot therefore be distinguished experimentally. That this claim is false is shown by equations (40) and (42) which summarize the different predictions of the two “interpretations” concerning further measurements on subsystems one of which has completed a measurement on the other.

https://pdfs.semanticscholar.org/c948/44bc9128e77077abdf36a6...

I judge by the fact that there aren't very many people doing experiments meant to distinguish the various proposals that physicists continue to generally believe there isn't much that can be done to distinguish the various interpretations from each other. Given the incentives to complete such an experiment and even just eliminating one possibility (even if one couldn't nail down which is true), and the fact that it seems to me many of the possible experiments that could do this are more lab-bench style experiments with a laser and a handful of mirrors and electronics rather than Large Hadron Collider-class experiments, I'm guessing the idea that the theories are distinguishable is a minority view, and one that the minority has not yet managed to do something so compelling with that the majority has no choice but to take note.

The specific experiment proposed by Deutsch is not yet possible to perform in practice.

Proving nonexistence is impossible because there is an infinite number of possible explanations for how the multiverse can exist without being able to be proven, and that these explanations can themselves require proof of nonexistence.

The premise of proving nonexistence is the wrong way to assess credence of a theory.

Likewise, proving existence of multiverse is as impossible as proving nonexistence for the reason that the multiverse is postulated as existing independently in an infinite number of permutations that can not interact with each other. If multiverse permutations can exist in the same time and space as another permutation, then matter and energy are supposed to exist in infinite number of states simultaneously, and would be impossible to measure.

This is the same argument around the existence of "God". It is not possible to prove God's nonexistence. Similarly, it's unlikely to be possible to prove God's existence and thus the debate continues.

On the nature of God, I read a theory that God is "truth", and thus any being that comprehends all truth is essentially God. In our human quest to gain knowledge of the truth of the universe, we have developed the ability to accomplish things that hundreds and thousands of years ago would have been considered God-like.

In 13.7 billion years of the existence of the universe, is it not possible that some entity was able to obtain sufficient knowledge of the truth of reality (laws of nature) to be indistinguishable from "God"?

Any place you can travel to is by definition part of this universe. According to the multiverse hypothesis, any mathematical structure is a universe. For instance, "the locus of points equidistant from a given point" is one of the universes. You cannot travel there; that universe has no way to accomodate a representation of you, let alone a representation which could record the experiences of being in that universe and then travel back to tell about it.

> if somebody traveled to one and thereby disproved me

That person would have to travel back as well, thereby making this proof doubly hard :-)

Conscious thought requires a delicate interplay of neurons and chemicals, that if disturbed by visiting a permutation of the multiverse, would cease to function.

Humans can not directly observe an alternative permutation, but even if they could, how would they be able to find their way back to their original permutation if there's an infinite number of permutations?

"Conscious thought requires a delicate interplay of neurons and chemicals, that if disturbed by visiting a permutation of the multiverse, would cease to function."

The multiverse need not have different physical laws; the quantum multiverse if true, for example, is basically our universe just viewed from a different point of view.

"Humans can not directly observe an alternative permutation, but even if they could, how would they be able to find their way back to their original permutation if there's an infinite number of permutations?"

Unsurprisingly, science fiction authors have pondered this for a while, and one popular answer is a travel machine where part of it still stays in the universe of origin, so returning home is like pulling a rope back in. Even if we're in a quantum multiverse where the source universe and the destination universe are continuing to fuzz, you can still imagine there's some sort of correspondance that means that any given individual will still have a uniquely-corresponded universe to travel home to.

I believe this is all technobabble bunk since I doubt it can correspond to any possible real configuration of atoms and energy, but, like I said, someone could well prove me wrong by building one, and that would be that.

If every action that can happen, does happen, then the "universe" that you left only exists in that exact moment of departure because every quantum interaction from that point forward creates more branches of infinite universes. Thus, which of those would you return to? You could only return to the exact moment you left or to some random branch that's created after you leave.

Maybe you can just observe something coming out of an alternative universe into yours.

Maybe you could go in an alternative universe that is different, but not different enough that it prevents you to function.

The absence of observing someone or some object to date suggests that multiverse can not be observed or can not exist, because if it was possible to observe or if it did exist we would have seen some evidence of it by now.

In an infinite universe, there should be constant evidence of multiverse apparent.

In an infinite universe, there are an infinite number of variation of universes with properties implying any given of event happen 0, once, rarely or often.

That's the problem with the infinite universes theory. You can pretty much make up whatever you want, it answers to any question.