There's a diagram on the wall at one point near the end - can't remember if it was in Rapture or on Comstock's ship - that explains it. It's just a little branching structure showing the path Booker/Elizabeth took through the various parallel realities.Cass wrote:
Question regarding tears: So when Elizabeth is opening tears in Fink Manufacturing to find Chen Lin, do you completely leave behind the world you started in? She opens a tear to a world in which Chen Lin lived, but... do you ever get back to the original world, or do you just hop from world to world? You seem to end up in a world where the Vox Populi have the guns you need, but is that the world you started in? Or does it not matter? That part just made my head hurt.
Basically they move into a new, separate reality every time they step through a tear. So, for example, in the reality you're in when the game starts, Elizabeth and Booker disappeared into thin air at one point and that universe continued without them. At the very end of the game, Booker and the various Elizabeths return to an earlier point in the timeline to stop Booker ever becoming Comstock and so erase everything that happened after that point.
I like what they did in that closing shot, with the musical cue playing every time an alternate Elizabeth disappears. Elizabeth is left alone and the screen goes black before the last note plays, similar to the spinning top from Inception. I guess whether or not she blinks out of existence entirely is dependent on if she was conceived before or after Booker refused to be baptised? Our version of her can't exist, since she's been shaped by events that only occur if Booker lives, but it could be argued that there is an Anna or an Elizabeth somewhere.