Apparently there are any number of other realities in the Star Trek multiverse (if that's the right word) but a post by KingDaniel about the writer's intentions (as opposed to what we saw in STXI, which seemed ambiguous) got me thinking.
I think KingDaniel is correct. That is what was supposed to happen, however ...
When Nero went back in time (to year 2233) his arrival split off a new reality, which the movie proceeds to follow. But when Spock is sent back to year 2258, his arrival, to be consistent, would split off another new reality, also from the original prime universe. In other words, from the universe without Nero, not the one Nero's arrival created and in which he now lives.
As far as I can see, what we would end up with is (1) the prime universe, (2) the Nero universe and (3) the Spock universe. The last two, splitting off from the same prime universe, but 25 years apart.
It seems to me that red matter black holes would either send objects backward in time to the same reality, or to a different one selected presumably at random (splitting off a new universe in either case). But how (apart from the requirements of the plot) could they transport Spock to Nero's reality? To a specific but different universe from the one, said object, started in? I just don't see how it's possible for Spock (and red matter) to end up in Nero's new universe except by a nearly impossible fluke given the practically infinite number or universes that must exist.
Nero went back in time from 2387 (8 years after Star Trek Nemesis) to 2233. Despite updated visuals this 2233 is supposed to be, up until the "lightning storm" that diverted the Kelvin, the same timeline as TOS/TNG and the rest. By altering events Nero created an alternate timeline. It's that alternate timeline that Spock Prime emerged into in 2258.
I think KingDaniel is correct. That is what was supposed to happen, however ...
When Nero went back in time (to year 2233) his arrival split off a new reality, which the movie proceeds to follow. But when Spock is sent back to year 2258, his arrival, to be consistent, would split off another new reality, also from the original prime universe. In other words, from the universe without Nero, not the one Nero's arrival created and in which he now lives.
As far as I can see, what we would end up with is (1) the prime universe, (2) the Nero universe and (3) the Spock universe. The last two, splitting off from the same prime universe, but 25 years apart.
It seems to me that red matter black holes would either send objects backward in time to the same reality, or to a different one selected presumably at random (splitting off a new universe in either case). But how (apart from the requirements of the plot) could they transport Spock to Nero's reality? To a specific but different universe from the one, said object, started in? I just don't see how it's possible for Spock (and red matter) to end up in Nero's new universe except by a nearly impossible fluke given the practically infinite number or universes that must exist.