I'm not a big fan of parallel worlds, alternative universes and all that. They worry me.
They're fun, though. Comic books, I gather, have been using them for ages, letting heroes meet each other, showing the readers what would happen, and then going back to the established universe. The reset button gets pressed and everything goes back to normal.
The reset button gets pressed a lot in Star Trek. Kirk let's Edith Keeler die, in one of the most beautiful Star Trek episodes ever, and the world he knows comes back. But, for a while, a different world existed, and it existed for three hundred years until Kirk went back in time and let Edith die, but it only lasted three hundred years for a moment. The centuries only lasted for moments from the point of view of the crew standing by the Guardian of Forever.
So where was that time? There was the matter that made up that world, the people, the planets, the energy that made up that world, where did it all go?
Maybe it went to the Mirrorverse. Now that's a fun place to visit as a writer or reader, (I wonder how the Mirrorverse coped with the Borg - who would have been the good guys there) but I wouldn't want to live there.
In another encounter with the Guardian of Forever it turned out that Spock died at the age of seven, and then his mother died in a shuttle accident on her way back to Earth after his death. Yesteryear was one of the better of the animated ST shows. Spock has to go back in time and save himself. This means that the first officer who replaced him has to give up his place in that history. Where did he go? Has he given up his existence entirely in the established ST, or is he having a career somewhere else?
The idea of parallel worlds is that everything happens in a universe of it's own. For every coin that gets tossed, there's a universe where it came up heads, and another where it came up tails. There's a universe where Nero never burst through back in time to kill James Kirk's father, and there's the universe where he did. Either way, James Kirk became captain of the Enterprise.
But here's the thing. It happened differently. Instead of suffering through the events of Kodos the Executioner, and becoming a hero on the Farrugut, Kirk has come straight from disgrace over the Kobayashi Maru test to the captain's seat. Spock had to order him out of it.
In the original series we watched Kirk and Spock form their friendship. In the new Trek, they're friends pretty much because old Spock told Kirk that he should be, and that Kirk should be the captain. Should he, though? In old Spock's experience, bad things happen when the known trail is left, but really would it matter if new Spock was captain instead? Should new Spock take his own advice and stay with the Enterprise
The altered timeline has also altered Spock's relationship with his father. In the original series, Sarek refused to even speak to Spock, who had lowered himself to join Star Fleet. Not only that, but Spock seemed to have been taught that emotions were dirty and he shouldn't be having them. In the new universe Spock seems to be quite happy. He's got a relationship with Uhura that gives him no inner conflict at all, and while they are reasonably discreet, nor do they really hide it. If the coming series of movies decided to go back in time and reverse what Nero has done, thus saving Vulcan, Spock would presumably lose all this.
The point is that by coming together so easily, they didn't have to make any difficult choices. Kirk didn't have to kill Gary Mitchell and Spock didn't have admit to mourning him also. When ST was telling little morality tales, when the characters made their choices, their relationships gained weight. Now it's gone.
So now the main crew are all together all at once. Neither Rand nor Chapel are there, but maybe they were off screen. Chekov is there where before he arrived later. Now that the characters have accepted their places, we have to wonder where the weight of their relationships went to. At the moment, they're like kids who happen to be on the same bus.