Usually, in Star Trek, when there's a timeline change, the indication is that the original timeline is gone and replaced with the new one. In City on the Edge of Forever, Kirk makes a comment that if they don't get the timeline straight, that millions of people who never died before will die.

Much of the time travel in Trek created suspense by declaring a need to restore the original timeline.

It's already been discussed in other questions about how, in the new movie (simply titled Star Trek with no subtitle or series number) they were unable to restore the original timeline. While some of this is open to interpretation, it seemed like in this instance, for the first time, in Trek, there was an alternate timeline that was seen as an alternate possibility - no reference was made to it replacing the original timeline.

In this movie, was there any reference to the original timeline still existing? In this movie, was the original timeline still considered to be intact?

  • I believe it was Spock who said that "millions will die who did not die before". Commented Jul 16, 2012 at 22:48
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    All I can say is: It had better have. Commented May 6, 2013 at 23:08
  • At issue really is why did 'old' Spock give up on finding a way to change things back? They didn't give up when they found the Guardian of Forever and had to change things back to prevent millions from dying that did not die before...so it's likely this reboot won't last very long. I wrote a mini-book that I posted in my blog on how it COULD be changed back. Because other events didn't take place that had an impact on the past, prior to the event that brought Nero and Spock to the past.
    – user14861
    Commented May 27, 2013 at 18:32

14 Answers 14


To say Star Trek is inconsistent with time travel would be a massive understatement. Each story involving it usually has its own rules which are established or inferred during that story. This is part of the nature of having a science-fiction dynasty where dozens of writers contributed to the canon.

That said, the writers of the film Star Trek sought to reboot the franchise while respecting the original canon we all enjoyed. As part of the reboot, they had Spock and Nero's actions create a new timeline that's similar, but crucially different from the original. This was meant to be irreversible, as to establish a new canon. In addition, they sought to do this in a manner that shows the original canon still exists.

The mechanism they used for this was Spock. By having the original Spock get hurled back in time into this alternate timeline, the writers show us that the stories we grew up on are still there, but they're inaccessible to this new Enterprise crew. Otherwise old Spock wouldn't be the Spock we knew from TOS and TNG, as his memories would have been presumably overwritten with the new historical events of the film. During the film, there's a scene on the bridge where they establish this in-universe:

Spock: Nero's very presence has altered the flow of history, beginning with the attack on the U.S.S. Kelvin, culminating in the events of today, thereby creating an entire new chain of incidents that cannot be anticipated by either party.

Uhura: An alternate reality.

Spock: Precisely.

In addition, the makers of the game Star Trek Online, which takes place in the original timeline, released this image which helps clarify where their game fits into the new status quo. Timeline of key Star Trek events

The 'Alternate Timeline' being the one of Star Trek (2009). This nicely lays out how the two timelines are related, and shows they both continue to exist.

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    I have to disagree. Far and away, it's more common to see time travel as a means or method of altering/restoring the universe Trek operates in. Otherwise, you have to label dozens of stories as fundamentally futile; Star Trek IV, Yesterday's Enterprise(TNG), All Good Things(TNG), City at the Edge of Forever(TOS)… all of them were exercises in futility, because they didn't revert the universe to its previous save state; the time-traveling character(s) simply leave 'actual' Trek universe and create a new one with each time travel event.
    – Stick
    Commented Dec 26, 2013 at 19:37
  • The interfering also caused changes in the past different from the main universe, for example Khan's origins are vastly different from the old movie to the new one... In one he rule most of Earth in the 90's... in the new one he had been in stasis since approximately 1959.. Commented Jan 6, 2014 at 15:19
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    TNG: Parallels showed us that a vast number of parallel universes already exist as Worf travels between the different timelines. Eventually they temporarily merge and hundreds or more versions of the Enterprise appear. Commented Jan 18, 2014 at 22:40
  • They should have explained it more. As written by others, in every instance of time travel in Star Trek until now, alterations of the past overwrote the timeline and the alterations must have been undone by the hero of the day. Why should it be completely different this time? And how should Spock know about it? That he still exists with his memories intact is no proof, this also happends to the heroes who fixed the timeline before. So why does Spock not take a warp capable ship, time warp to the past, anihilate nero, restore the old timeline and timewarp wo his own present in his own timeline?
    – Hothie
    Commented Feb 23, 2015 at 10:58
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    Khan's origins as of STID are meant to be the same as in the original series. He was not said to have been in stasis since 1959. He was said to be 300 years old. There's a difference. He predates the change in the timeline so his origin would not have been changed. Commented Jul 10, 2015 at 22:42

This is one that's tough to handle in universe because the answer is complicated by Star Trek's inconsistent policy regarding temporal causality. In Star Trek it has never been the case that the moment you cause a causality shift in the past, all the future is changed forever.

Obviously for storytelling purposes, there's kind of "some leeway" where the future has time to send people to correct it - vis a vis temporal agents. It crops up in DS9, Voyager, TNG, Enterprise - but the classic example is in Voyager's "Relativity". You see this timeship from the future constantly meddling in instances throughout Voyager's timeline in the Delta Quadrant. But obviously when they go back to the scene with the Kazon attack and Present!Janeway stops and interrogates Seven of Nine, from that instant on, PERMANENTLY changing the future, the set of causal circumstances that led to the Temporal Agents' incursion to set things right in the first place was not wiped from existence. In fact on the contrary, you have real time communication going on between this Timeship Relativity in the future, and Seven of Nine in the past, actively having a conversation with Janeway that never actually happened -- an event that should, for all intents and purposes, be the equivalent of the grandfather paradox, since "Seven of Nine having a conversation with Janeway in the past" permanently alters the future. Certainly Voyager's future, and the entire galaxy's future in the context of the development of the Timeship Relativity and its mission, to a lesser extent.

So to answer your question, I would say it's fixable because in Star Trek terms, there's always "time" for the Temporal Police to swing into action and set things right. In essence, they're kind of 'top level' looking down on all these incursions into time "below them". Based on the way it's portrayed in Voyager and Enterprise, it would seem like a foregone conclusion that at some point the Temporal Agents would be able to just go back in time, appear between Nero's ship and the USS Kelvin, and totally smoke Nero in the dick. Just end the incursion right then & there. The only other alternative would be to go back to 2391 when Spock failed to save the Romulan sun - and to fix it for him so that Nero's never compelled to go back in time.

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    I wasn't asking if it was "fixable." I was asking if the original timeline was intact -- was the alternate one a fork, or did it replace the first one?
    – Tango
    Commented Feb 12, 2012 at 6:11
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    +1 for 'smoke Nero in the dick'. I can't stand this application of time travel as the catalyst for an alt-universe in Trek.
    – Stick
    Commented Dec 26, 2013 at 19:28
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    @Tango: he's suggesting that the alternate timeline is a "fiction" because the old one is fixable, so it "will be" fixed, so the original timeline is the "only" timeline that matters. This actually makes sense to me -- compare the Temporal Cold War in ENT.
    – nomen
    Commented Apr 10, 2014 at 22:50

See, this is kind of a giant problem when it is weighted against major time travel stories in the Star Trek universe. Time travel in Star Trek is not nearly as 'unpredictable' as other posters here have said (at least not while Roddenberry was around; someone started playing a little fast and loose once the old boy wasn't around to flick them on the ear).

Consider the following:

In The City on the Edge of Forever, all involved parties - Kirk, Spock, and the Guardian - treat time travel as if it threatened to undo their past and alter their present.

"Captain's log, no stardate. For us, time does not exist. McCoy, back somewhere in the past, has effected a change in the course of time. All Earth history has been changed. There is no starship Enterprise. We have only one chance. We have asked the Guardian to show us Earth's history again: Spock and I will go back into time ourselves, and attempt to set right whatever it was that McCoy changed."

  • Captain Kirk

"Time has resumed its shape. All is as it was before."

  • Guardian of Forever, after Kirk, Spock and McCoy return

Much later, during the events of Star Trek IV: The Voyage Home, Spock himself suggests a solution to the probe's signal by way of traveling through time.

Spock: "There is one possibility, but I cannot guarantee success. We could attempt to find some Humpback Whales."

McCoy: "You just said there aren't any, except on Earth of the past."

Spock: "Yes doctor, that is exactly what I said."

McCoy: "Well, in that case... Now wait just a damn minute."

Kirk: "Spock... start your computations for time warp."

This idea of time travel representing a literal historical change to the same Universe the characters exist in before and after the time travel event is maintained moving forward - TNG never mentions time travel as anything but a tool for altering and/or restoring the state of previous events.

During the events of Yesterday's Enterprise, Data makes the following assertion:

Natasha Yar: I've been working with one of the officers on the Enterprise-C. He's, he's nice, I, I like him. I'm worried about what's going to happen to him. Lt. Commander Data: We may never know what happens. If they succeed, we will not even realize that these events occurred.

There are many, many other instances of time travel in TOS and TNG, and moving forward into DS9/VOY/ENT it even becomes a critical aspect of the storyline, so much so that a Temporal Prime Directive is eventually brought into the franchise as a means of addressing the convenience factor. After all, if all you need to do now is configure the warp nacelles to emit chronometric particles in tandem with your warp field, every Starfleet vessel is essentially an interstellar DeLorean, so nothing has to be impactful or meaningful. Data dead during Nemesis? To hell with that; let's just send one Enterprise a week into the past for the next 26 weeks until the Scimitar is assaulted by so many Enterprises that it never even leaves Reman orbit.

Here's the problem, then - introducing JJ Abrams's script into the mix takes the majority of the rules set up to try and address this, and just tosses it in the trash. It not only creates a separate set of rules in an alternate universe which somehow brought Old Spock over from the original universe, but if it is to be accepted as canon actually makes Spock into a lousy scientist and even challenges Data's knowledge of temporal mechanics.

After all, why bother traveling through time for all those whales if it's just going to create a new universe where the only thing that's different is Gillian and two whales aren't in the 80s anymore? Why bother with the Borg time traveling to April 2063; just casually side-step the temporal wake, remain in your own timeline; apparently the Borg just ragequit and signed onto a different server where the difficulty settings aren't quite as high.

Unfortunately, this is one of those things where they cannot both be equally applicable: one method of time travel is a ticket to Retcon Central, and the other kind is spawning multiverses.

Whether or not there is a multiverse in Star Trek is not the problem; there are indeed parallel realities that come up once in a while, most notably TOS's Mirror, Mirror and Worf's cat-assing around from the TNG episode Parallels. Time travel isn't really the right key for the lock, though.

Of course the real issue here is that it's just a reflection of the reboot writers' lack of attention to detail regarding their subject material, and it's one of dozens of differences that are tangible (and IMO, problematic at best) in JJ-Trek. If nothing else, the three movies that play with time travel are easily accessible and go a long way towards indicating that they are "setting things right" instead of "copying and pasting in a new universe". So really, if you're going to play it close to the vest, Old Spock goofed things up pretty bad when he Jellyfished back to the future. Maybe in New Trek time travel is a nice and tidy method for sandboxing the reboot, but he left from the Old Universe -- and it's pretty clear that it's tantamount to Control-Z in Old Trek. If a new universe was indeed created, it came at a staggering cost.

  • Staying with your Old Trek example, in the timeline where they didn't go back, Earth was destroyed by the probe. So, if the timeline is split in two at the point of their (arrival or not) in the past, in the original Earth dies and in the new it survives (less Gillian and two whales in the past). You could have both timelines merge back when they return to the future, and that's the best way I saw to resolve this problem so far, in ST universe, without making everything pointless (suggested in the ST:DTI book series). This solution won't work in New Trek, though. Commented Jan 8, 2016 at 19:33

It's an alternate timeline. A new timeline branched off when Nero entered. It's said in the dialogue, as has been noted. And writer Bob Orci has said it repeatedly in online discussions with fans. Life after Nero and original Spock left (and everything before) kept going. Apparently. Trek previously showed plenty of alternate realities, like the Mirror Universe. Why didn't Nero just warn Romulus that a star was going to destroy it in 130-odd years, or just destroy the star himself? Because he's crazy -- and maybe he thought he had plenty of time.


The prime Star Trek timeline still exists. It is well established that alternate timelines can branch off of a prime reality without destroying the original. This is proven in both in "Mirror Mirror" (TOS) and "In a Mirror Darkly (parts one and 2)" (ENT). The alternate timeline in which the Terran Empire exists in place of the Federation split from the prime reality in 2063 when Zefram Cochrane killed the first Vulcan that officially made contact with humans. This is obviously completely different than what happened in the prime reality. This split in time shows that alternate events can lead to alternate timelines, but that does not mean that this split in time destroys the prime timeline. There are other instances of course, where the original timeline is destroyed [EX:"Year of Hell" (VOY)], but the timeline in which Star Trek (2009) occurs does NOT destroy the original timeline. From the real world perspective: do you really think that JJ Abrahms would have made his movie establish that all other events in the prime reality never occur? I agree that occasionally, Abrahms does not hold true to the true Star Trek principles, but not even he would do something as sacrilegious as destroy the original timeline of Star Trek.

And if that doesn't prove the fact that the prime reality still exists, please be reassured by this, which is taken from Memory Alpha (the Star Trek wiki): The writers of Star Trek, Alex Kurtzman and Roberto Orci, were asked about the implications of the new alternate reality that was introduced in the film in an interview. They explained the new reality runs parallel to the prime reality as a new quantum reality, as the concept was explained by Data in the episode TNG: "Parallels".

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    Can you add a short summary of Data's explanation?
    – Wilbert
    Commented May 7, 2013 at 15:24
  • youtube.com/watch?v=MzUEu7Gb7Cg
    – Luke
    Commented May 7, 2013 at 20:56
  • Basically, Nero's and Spock
    – Luke
    Commented May 7, 2013 at 21:01
  • 's actions caused the events in 2233 to occur differently. Kirks father was killed, which of course he wasn't in the prime reality. All these changes led to a new quantum reality, which although different does not disrupt the prime timeline
    – Luke
    Commented May 7, 2013 at 21:03

The original timeline is safe. The universe of the new movies is another timeline even before Nero arrives. The proof is that Kelvin's markings and that of her crews showed the Star Trek symbol that was only used by the Enterprise in TOS, all other ships and facilities had their own unique symbols.

Starfleet only adopted it for the whole fleet after TOS's 5 year mission. It was in TMP where the rest of the Fleet was shown sporting the symbol (except the Epsilon station).


It's an interesting grandfather paradox. All of the things that happened in the original timeline must have happened in order for Nero to want to change that timeline. However, what if he succeeds in finding a way to prevent the destruction of Romulus? Then none of the events that resulted in him going back in time would have happened.

On the one hand, Nero has his facts wrong; Spock isn't responsible for the destruction of Romulus by his actions. He's responsible for it by his late action. So, killing Spock won't avoid the supernova. On the other hand, killing Spock WILL prevent the Narada going back in time, thus creating the grandfather paradox; by killing Spock, Nero would destroy the very reason he's able to kill Spock.

The only resolution to the Grandfather Paradox that involves the possibility of killing your grandfather is a "multiverse". The original timeline and the alternate timeline branch at the moment the "lightning storm in space" appears in what had been the original timeline. In what we know as the original timeline, the Kelvin never gets a call to investigate, isn't destroyed, and Kirk grows up in Iowa knowing his father. In the alternate universe, the Kelvin gets the call, is destroyed, and Kirk grows up knowing what his father did as captain of a starship for 18 minutes.

  • Grandather paradox exists only if you look at time as a 2D line, which it isn't. It's more like multi-layered std::vector of data, existing "all at once", where content of one cell is calculated based on the content of the previous one "all the time". Change a value in the past by inserting another value, following data pockets will update, but the inserted thing will remain.
    – Petersaber
    Commented Jun 30, 2015 at 7:06

The answer to this is hard to explain...

  1. There are several forms of time travel in Star Trek.
  2. The form of time travel determines whether or not the future is preserved.
  3. If you go through and match up what happens with each the closest one to what happens in JJ Trek says that the timeline is overwritten. If anyone wants to go do this and argue about this, have fun. I've tried and saw it was pointless to use reason and evidence so I don't bother trying anymore with this stuff ^.^

So, if you follow just the TV shows and Movies then the right conclusion with regards to this if you follow the rules set down then the Original Timeline did not survive.

On the other hand JJ Abrams, co-writers, and CBS all deny this and say that the original timeline does survive and further the MMO Star Trek Online is canon within the Star Trek universe along with the movies and TV shows and supports this...

Will CBS maintain this with their 2017 series? No one knows... And people seem to ignore that all this might be moot anyhow considering Enterprise may have rewrote significant chunks of the timeline and made it so the "original" timeline didn't survive but oh well.


I don't know of any definitive indication of whether the original timeline still exists (whatever "exists" means) -- but I would argue that it could potentially be restored. (And whether restoring it would destroy the new timeline is another question for which I don't have an answer).

We've seen that the Federation of the distant future is able to perform time travel. If, say, a 30th-century Federation timeship were to go back in time and destroy the Narada as it emerges, or just prevent it from going back in time in the first place, then events would unfold as we saw in the Original Series.

Whether they would do so is another question; they'd be destroying several centuries of their own history, and probably creating more paradoxes.


Ambassador Spock did not lose his memory of the Prime Timeline. In fact in Into Darkness, Commander Spock calls his older self to see how to defeat Kahn, Ambassador Spock, after ruminating about timelines, gives his younger self the answer.


While not completely audible in the film, before being teased by his classmates, young Spock is asked by the computer in the learning center on Vulcan: "What is the central assumption of Quantum Cosmology?" To which Spock replies: "Everything that can happen does happen in equal and parallel universes."


I would like to think that the method of time travel that is used determines weather or not an alternate reality is created. In this case they used a black hole, so perhaps by using that means is a way that they can create an alternate reality, rather than completely destroying the old one.

Perhaps if the new Spock would die somehow and Spock Prime was not erased, that should prove that this an alternate reality and not an alternate reality.

I thought it would be a good idea that is some future spinoff television series that would have an episode that takes them into the JJ Abrams' universe, but at the same time take place post Nemesis. I think it would be awesome to an Abrams' version of the Enterprise-E or even see how Deep Space Nine was built.

But the movie made it clear, this is an alternate reality. Not everyone agrees with that, but the movie is canon and I take that seriously. I really would like to see a prime reality series again someday, but if they really wanted to they could also make an alternate reality series and run that side-by-side with the prime series and maybe even do some crossover episodes. And then even make a third "Mirror, Mirror" series and have them all take place during the same time.

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    I know what I am about to write here is non cannon, but I recently watched a fan film, called "Star Trek: Horizon", it is suppose to be the unofficial finale for Star Trek: Enterprise. They had an explanation on what causes a new reality to be created and that is if you try and change too much, too fast, that is when you create an alternate universe and keeping the original timeline intact. If you change things a little bit at a time, this where you can alter the timeline. I recommend watching this film, it is on YouTube and I would like to point out that I was no involved in that project.
    – Thylorion
    Commented Jul 5, 2016 at 1:33

It's impossible to say one way or the other. Now, don't misunderstand: I'm not saying it's impossible to know, I'm saying it's impossible to say, fundamentally.

The problem is that the definition of "exists" is too weak to cover this topic. By one perspective, only one timeline — ours — "exists"; by another, all possible timelines exist in parallel.

It's total folly trying to decide which one is "correct" because both are correct by different definitions.

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    The source material provides plenty of data suggesting that time travel does not 'produce' parallel universes, rather that it modifies the same universe that the time travelers depart from. The plot of movies such as Star Trek IV and First Contact are expressly contingent on this being so; otherwise the crew isn't saving Earth in either movie, they are simply side-stepping their universe and going to a more preferable one. By the JJ Abrams account of time travel, we never should have met Sela; never needed to retrieve McCoy from the past; and so on.
    – Stick
    Commented Aug 11, 2014 at 21:56
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    @Stick: No, not really. Parallel universes, in this model, fork at decision points so going back in time will easily result in the effects you exemplarise. In fact the source material is fundamentally incapable of suggesting this either way, as I've already described: we cannot directly observe alternate timelines without "entering" them; at that point the distinction of whether they exist or merely hold the potential to exist is entirely undecideable. It's the old "tree in a forest" thing. This is science/formal logic, not screenplay analysis. Commented Aug 11, 2014 at 21:58
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    That's interesting, but in a science fiction situation where suspense of disbelief has already been applied to time travel and the rules established within this particular franchise, there's no longer a need to guess. In Star Trek, ships can travel at FTL velocities, people continually maintain their sense of self during matter-energy transport, species from disparate worlds can occasionally breed, and time travel does not cause or lead to parallel universes - it alters the 'current' universe. I understand what you're saying, but it doesn't apply to Star Trek because 'suspense of disbelief'.
    – Stick
    Commented Aug 11, 2014 at 22:06
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    @Stick: "people continually maintain their sense of self during matter-energy transport" Oh man don't remind me of Realm of Fear -.- Commented Aug 11, 2014 at 22:23
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    @Stick: It's amazing what you can do when you don't exist Commented Aug 11, 2014 at 22:28

I'd say it replaces the first one. Spock seemed to allude to that fact in the movie.

Spock: Nero's very presence has altered the flow of history, beginning with the attack on the U.S.S. Kelvin, culminating in the events of today, thereby creating an entire new chain of incidents that cannot be anticipated by either party.

Uhura: An alternate reality.

Spock: Precisely.

That, to me, says that all events in Star Trek, from TOS to Voyager could be thrown away. It never happened.

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    Spock said it created a new chain of incidents, not that the old one was destroyed. And the word "alternate" could imply (though weakly) that the original timeline still "exists" in some sense. Commented Jul 16, 2012 at 22:51
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    @KeithThompson For example, TNG 7x11, Parallels.
    – Izkata
    Commented Jul 16, 2012 at 23:22
  • I would say Spock's use of "altered the flow of history" implies that it is indeed the same timeline and not an alternate parallel timeline.
    – Wayne
    Commented Jan 19, 2016 at 19:31

I have to disagree with most of the posts here. The planet Vulcan was destroyed and with it history changed. Plan and simple. It's as if Edith Keeler was allowed to live, delay the US entry to WWII and Hitler won the war. Only in this case the effect on history is much more extreme. This is not another quantum reality as portrayed in the Next Generation episode called Parallels. We will never see the prime timeline again.

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    Do you have a reference, quote, reasoning about why you think that?
    – Izkata
    Commented May 3, 2013 at 12:31
  • And yet this answer does not address my actual question at all. Even with things as you say, it could still be that the new timeline is only an alternate.
    – Tango
    Commented May 29, 2013 at 0:04

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