Future computational history maybe?After one measurement, your wavefunction contains 10 observers, unambiguously. That means each observer EXISTS with probability 1. Each observer has an amplitude associated with them, but no way to detect that amplitude. The common argument is that we have no reason to introduce a probability measure on this space. Probability of what?
I mean, if the universe didn't contain any operations that could combine to form computation at some scale, we wouldn't be here asking this question, so that has to be important somehow.
If you have an NDTM with observers in it, then two *different* observers can have memories of past observations that are in *literally* the same observations. Later on, both clearly exist separate from each other in the NDTM model. The model however, has clear distinction between branches, and so we are tempted to just draw the line there, but there can easily be analogue or continuous models that can encode an NDTM's operations (QM is perhaps even such a construct even at the smallest scales, we aren't sure yet) in which the "question what are we counting" becomes hazy. But the existence of the observer is still coming from the fact that it's modeling an NDTM, the fuzziness is just making things complicated (or perhaps, simpler) and... well... fuzzy. But even if no two observers ever become fully de-coupled in their possible interaction, there are still differing computational histories in the full description of the world (there are of course 'more' of them) and if there's a concept of history in a deterministic function, then surely there is also a concept of future. When an observer at T=n is multiple observers at T=n+k, then the observer at T=n cannot possibly be every observer at T=n+k, and must have some range of expectation for future past observations.
The only part that seems weird to me is explaining the actual probabilities we have been observing... why are they this, with undeniable repeatability, and not something else... or why this probability is coming from a term being multiplied by a complex number. I realize this is still one of the main objections to many worlds, I'm just saying I don't see why the existence of observers or having some probability associated with the wave function is strange. My gut reaction is actually that it shouldn't be using complex numbers at all, that they're just an abstraction over a deeper model that just works this way in the tests we've been able to bring to bear so far, which makes the probabilities observed and the complex factors reconcilable. We still don't have quantum gravity, and gravitons would be so much smaller than anything else that they might just reveal another layer of humdingery going on that the current model emerges from. That could (as in almost certainly is) just be my near complete ignorance of the field and general hopefulness talking however.