I think we were supposed to agree that future Janeway's meddling was ethically questionable at best, while there wasn't much of an issue with alternate Yar returning to the real past because that WAS the real past and the alternate was just the result of an accidental anomaly ("I'm supposed to be dead" presumes that the familiar timeline is the only one, aside from this accidentally-created, wrong one).
"Yesterday's Enterprise," if you follow the causality, showed the natural future in the absence of time travel -- i.e., the Enterprise-C vanished in a spatial rift created by a volley of photon torpedoes during a fight with the Romulans, and that incident inevitably led to the Klingons being at war with the Federation 20 years later. The disappearance of the Enterprise-C was a natural result of its fight with the Romulans, so everything that happened after that was the natural course of history in the original timeline.
New timelines are created only through time travel into the past (not vanishing and reappearing in your own future), so the familiar TNG timeline did not exist until AFTER Yar and the Enterprise-C went BACK in time, CHANGED the natural course of history, and prevented the Klingon war with the Federation. When the Enterprise-C initially disappeared, then reappeared 20 years later, it was in its own timeline, its own future, just like when Khan was frozen in 1996 and then awakened in his own future. Instantly appearing in your own future does NOT change history.
When the Enterprise-C emerged from the rift near the Enterprise-D, it was in its one true future, where the Klingons were at war with the Federation. Only after Guinan (who had already met the alternate-Picard in San Francisco in 1900 in "Time's Arrow," and in the Nexus in 2300 in "Generations") convinced Yar that she needed to go back and change history, did the crew decide to send the Enterprise-C back in time, thus creating a new timeline and altering the natural course of events.
Don't be fooled by the camera's point of view changing from one timeline to the other. It is simply following Lt. Yar's change from one timeline to the other. You cannot infer that one timeline erased the other, because the cameras left the original timeline at the moment Yar did.
But other times, such as in "Endgame" or "Yesterday's Enterprise" or DS9's "The Visitor," we see the original timeline play out for several decades, only to have a time traveler go back and make a major change, setting history on an entirely new course.
Certainly in YE the changing erased the timeline to set up a new one and I think that was also the intention with Endgame and The Visitor; the stories work better with a sole but changable timeline; if all Jake and Janeway were doing was making things better for alternates rather than the only real ones, I think that's less interesting and they'd have less motivation to do that.
In many "Star Trek" episodes, such as "Star Trek IV" and "
E2," the characters are shown having philosophical discussions about the nature of time travel, because, like you, they are not sure what the consequences of changing the past are.
So sometimes they may think and act like there is only one timeline, and they are "preserving" their own past (like Marty in "Back to the Future"), but other times, such as "Time's Arrow" and "
Parallax," the crew is simply going through the motions of fulfilling its own destiny in a causality loop (like Kyle Reese in "The Terminator"). In some stories, such as "Yesterday's Enterprise," "Endgame," "The Visitor," and "Star Trek XI," characters are intentionally changing history to permanently create a new timeline. In other episodes, such as "The City on the Edge of Forever" and "Star Trek: First Contact," one time traveler creates a new, "undesirable" timeline, causing another time traveler to go back and "undo" the changes (by making further changes in the second timeline), thus creating a third timeline that is "close enough" to the original.
Through all of these episodes, there is one common theme: The characters are not completely sure what will happen when they go back in time -- whether to change history, to maintain history, or to "fix" history. (This is an extension of the writers of any particular episode not knowing exactly how time travel works, and consequently the viewers cannot derive a clear understanding of the rules of time travel, since there aren't any.)
The characters are never sure whether they are in a causality loop (such as "Time's Arrow" or "Parallax") and thus must go back in time and do nothing just to maintain the time loop; or if they feel they are already in a "bad" timeline (e.g., old Jake in "The Visitor," Admiral Janeway in "Endgame," Captain Archer in "
Twilight," or Lt. Yar in "Yesterday's Enterprise"), then they must go back and actively change history, in order to create a more desirable future.
Like the viewers of the episodes, the characters are just making decisions based on the limited information they have at the moment. Each temporal anomaly, time vortex, Guardian of Forever, slingshot effect, spatial rift, or red-matter black hole has different properties, so the characters have no idea what the consequences of their actions will be until they reach the other side.
Saying "there's only one timeline" and that time travel erases one's own past in ALL cases is just speculation and opinion on the viewer's part. The characters in some episodes may SUSPECT that this is how time travel works, but once they are in a new timeline, they have no way of measuring whether it is the same one or an identical one.
It has never been determined one way or the other, since the cameras invariably follow the time travelers into the new timeline, so we, the viewers, have no way of knowing whether the original timeline kept going without them, or vanished completely. From the characters' point of view, it doesn't really matter, since the time travelers always continue on with their missions in whatever timeline they end up in, and the cameras follow those new missions as if that is the only timeline.
There have been some ambiguous episodes, like the Vorgons in "Captain's Holiday, where the cameras follow them back into a new timeline repeatedly, but we have no way of knowing which is the "real" TNG timeline, or whether all timelines are part of a causality loop or multiple alternate realities.
In all of "Star Trek," there have never been two episodes where the same laws of time travel apply. Even where similar methods of time travel are used, each episode has some complication, such as two different time travelers on conflicting missions, travel into both the past and the future, being caught in a causality loop, traveling into an alternate reality and trying to get "back," or consciously changing the past in order to put right what once went wrong.
There is no episode where the characters say, "Well, this is what happened the last time we time traveled, so we just have to do the exact same thing again." No, every instance of time travel in "Star Trek" is unique, and has different, unpredictable consequences for the characters. The writers of the episodes clearly have no idea what "laws of time travel" they are trying to adhere to, which is reflected in the confusion of the characters in most episodes, resulting in all these ongoing debates about timelines on TrekBBS.
How does XI continue in the universe if it just kept some of the characters and concepts? It seems to me to be saying that the universe was too complex and established to write good stories in. This new universe can only be so much developed in a handful of films, especially if the filmmakers become interested in nostalgia.
This was really the only way for the writers to accomplish two goals: To use the classic, original characters again and recapture the spirit of TOS, while at the same time, telling new, compelling stories with real consequences and suspense, where neither the characters nor the audience knows what will happen next.
How monumentally boring would this movie be if this were just a "Star Wars"-style prequel, and Earth and Vulcan were threatened, but the audience already knows that both planets would still be safe in the 24th century? There would be no jeopardy, no danger -- just like we know young Anakin Skywalker would survive the pod race in the "Star Wars" prequel, because we already know how he dies in the future.
The writers only had three other choices:
- To tie their own hands and limit the creative potential of any story by making this a strict prequel, so the characters would just be going through the motions, and would never be in any danger.
- They could have just continued the series into the 25th century, where the Federation has "magical" technology such as transwarp beaming, invisible cloaking suits, personal wearable transporters, ablative starship armor, transphasic torpedoes, sentient mobile holograms, no real adversaries left in the Galaxy, and 300 years of history that would only be known to the geekiest über-fans.
- They could have just done a complete re-boot like "Battlestar Galactica," "Batman," James Bond, and every "Punisher" and "Hulk" movie, where just the title and some characters are the same, but new history and characters are created because the previous series contiunity is deemed "hopelessly contaminated and unrecoverable." But "Star Trek" does not fit into this third category, because its continuity, while bulky and convoluted, is still valid and has never been fully abandoned, unlike those other franchises.
"Star Trek" is unique, in that it is both an ongoing TV and movie series, and both follow a common continuity, unlike other series like "Smallville" or "Terminator," which had no connection between the TV stories and the film series using the same characters.
Like classic comic books, "Star Trek" has been continuously relevant through the decades. The "Superman" comics may have started in the 1930s, but he is still relevant and current a century later, and most of his comics follow a common continuity (across multiple timelines and alternate realities).
Very few fictional worlds can claim more than 700 episodes telling an ongoing story. Some, like "Robin Hood" or "King Arthur" or "Galactica" or "Batman" or James Bond, have a few strong characters or ideas that transcend one particular format or story, so they are continuously recycled or reimagined. "Star Trek" has always been about the ongoing narrative from one episode to the next, with a common history linking all the various series and movies, rather than just recycling a few iconic characters and ideas through multiple unrelated stories.
"Galaxy Quest" showed how "Star Trek's" characters, plot elements, and technology could be re-imagined and used to tell a completely new story without being part of the ongoing continuity. But Paramount's ongoing canon of 700 episodes has an enduring appeal, so there is no reason for the producers to abandon it. They are free within that canon to go back in time, create alternate timelines, introduce new villains, etc. -- but that has been true in each of the previous 735 episodes, too. Like "The Motion Picture" or "The Next Generation," this new movie series is just updating the franchise for a new generation of viewers, while keeping the ongoing narrative alive.
