This has been driving me nuts. For most of Star Trek’s history, the Prime timeline holds together no matter what happens to it. Kirk jumps around, Picard gets stuck in time loops, Janeway rewrites entire centuries, and the universe just snaps back like it never happened. Time feels elastic but stable.
Then Nero falls through a black hole, and everything falls apart. The Kelvin event doesn’t just make a new branch going forward. The ripple hits both directions. It rewrites history that should already be set. Starfleet looks different. Vulcan feels different. Even the technology and design philosophy seem changed long before Nero was ever born. That sounds less like a branch and more like time itself got rewritten.
Once that happens, the Temporal Prime Directive starts to fall apart. It only works if time moves in one direction. You can “fix” something when there’s a clear before and after. But if the ripple goes both ways, there is no original timeline to go back to. The moment the Kelvin universe forms, the concept of Prime reality stops being a single point.
And that’s before you even touch the Mirror Universe, which is not a branch at all. It has been running beside the Prime since the beginning. So now we have at least three full continuums: Prime, Mirror, and Kelvin. But that’s not the end of it. The Star Trek Online timeline exists as an extension of Prime, playing out events after Nemesis and even connecting to the Temporal Cold War. The licensed novels follow yet another line, continuing after Destiny and Coda, where the multiverse literally starts to collapse under the weight of too many versions.
So what is the Federation even supposed to do with the Temporal Prime Directive at this point? Which universe counts as the real one? Do you merge them? Do you pick one and call it Prime? Or do you admit that every version is its own living reality with its own moral weight?
Maybe the point isn’t fixing anything anymore. Maybe the Temporal Prime Directive is just damage control. Once time starts rewriting itself both ways and spawning whole new continuums like STO or the book universe, there’s no putting it back together. The best you can do is keep the pieces from smashing into each other and hope reality doesn’t collapse under the strain.
This isn’t quite true. Most of the time, Star Trek asserts that time travel to the past can and does alter the “prime” timeline - this is directly observed in “Past Tense” and “First Contact” (the movie, of course), when crew members who are protected from the alterations see reality warp before their very eyes. In those cases, the time travelers are forced to do what they can to “repair” history and get events to play out reasonably similar to how they orginally had. I assume things are still different, but they’re considered “close enough”.
This is a little contentious, but I agree with this interpretation, even though the actual films are pretty vague on exactly how the alternate reality came to be. It’s certainly a contradiction of basically every other depiction of time travel. But hey, it was a unique circumstance.
TNG’s “Parallels” deserves a mention as well, since it states that their are infinite parallel realities (and we see a bunch of them).
In general, here’s what I think is true:
An infinite number of quantum realities exist. These have nothing to do with time travel, and simply…are.
Time travel to the past can, and usually does, alter the future. Separate quantum realities are not created. These are the situations that the 26th century Federation time cops are concerned with.
The Kelvin Timeline seems to be an exception to (2), though I suppose there’s a possibility that Spock and Nero simply tunnelled over to a different quantum reality, in addition to travelling through time. This is 100% pure fanon, though.
I think that is what bothers me most about the Kelvin timeline is it seems not to conform to the Prime. The only way I can square it is that the trip through the blackhole not only went back in time but to a different reality.
It bugs me a bit too, but I guess there’s nothing really wrong with it being “the exception that proves the rule” - something extraordinary happened in that case, unlikely to repeat.
And the pre-existing time travel rules weren’t exactly clear-cut, either - my original response glossed over bootstrap paradoxes like “Time’s Arrow”, where the characters travel back in time because they found Data’s head in San Francisco, which was only there due to said time travel.
But then, from the perspective of people in the future, I suppose all time travel events look like bootstrap paradoxes…