Re: How would Sarek explain Spock 'Prime' to the other Vulcan survivor Especially since the time travel stuff in previous Trek made sense. ENT, "In a Mirror, Darkly" is the perfect example. The Defiant gets thrown back in time, AND into a parallel universe. Each universe has its own timeline. You can cross between universes (they did it in every Mirror Universe episode, Worf did it in Parallels), you can travel along the timeline of each universe (slingshotting around a sun, what the Borg did in First Contact, etc...), and in special cases, like that ENT episode, you can travel back in time and step into a parallel universe. Same thing happened in this movie, but Orci just doesn't want it to acknowledge that, although it's so easy and hurts no one.