In esoteric Buddhism there is a concept called ‘無戯論,’ which translates to something like: “no-vain speculation” or “no-mendaciousness,” or more fancifully, “no frivolous theorizing.” What it means is something like this: There’s no use talking about things that never happened, and saying things like “If only Xt…” and so on. Because if only event Xt happened at time t, it would be absolutely impossible to say how Xt would have impacted X2t at time t, and so on as far as the empirical, nonlinear, deterministic domino-principle goes, which exponentially reaches Chaotic Butterfly-Effect proportions like an utterly unpredictable wildfire.
If Xt had happened, perhaps you wouldn’t be here now to talk about it. To give a crude example: We played the lottery, didn’t win, rued the day, and fantasized about what we would have bought, the peace of mind the money would have afforded, and so on. But there is absolutely no way to tell, except without utterly vain speculation (because it never happened), as to what might have been, and what could have happened.
It is the very non-event that shapes the present, and thus, the present of the three worlds of the past, present, and future is sustained by not just the wave-collapsing events of the past, but also by the uncollapsed infinitude of probability waves of things that could have been but never happened.
The uncollapsed wave-function branches forth into a multiverse, but in the backdrop of Dark Matter, it becomes the larger, “unseen” multiverse of non-events, i.e., non-events which would have made for other, infinite versions of the current world, had they happened. This set is the set of vain speculations, the what-ifs, the if-onlys. The number of uncollapsed wave-functions, then, are literally infinite, and they are the very multiverses of orthogonal probability waves; metaphorically they are exactly akin to Dark Matter, for it is said that there is more Dark Matter in the universe than the “visible” universe itself.
So while the collapsed-wave-function universe, i.e., the “visible” universe is singularly the collapsed “particle” of the cosmic-quantum wave-function, the unseen wave is an infinite multiverse of potential fields of what could have been. The familiar universe collapses into the default of Being with respect to chreodes and cosmic Habit, and it is a cosmic “particle.” But the field of probabilities, on the other hand, contains every potential event which did not happen, which brings us back again to the idea of the Black Swan. Everything we experience is a result of an infinitude of non-events, and those non-events are the unobserved multiverses of the many-worlds-interpretation. They are unobserved because they never were, they never happened; otherwise the simultaneity of observation would have dragged them out of probability mode into the realm of actuality, viz., our familiar one world, the universe as it currently flows.