It seems that the writers and directors of Avengers: Endgame disagree about the nature of the

time travel

in the film.

At the end of the film,

Steve Rogers "returns" the Infinity Stones to the various points they were retrieved from.

Under the interpretation of the writers, i.e.

removing an Infinity Stone is the only thing that creates a (persistent?) branched timeline

the motivation to do this at the end of the film makes some sense - these

branches could be unnatural/damaging to reality, and bringing the Stones back to them stops them existing or re-integrates them with the prime timeline somehow.

However, under the interpretation of the directors, i.e.

any change to the past creates a branched timeline

the motivation to do this makes a lot less sense.

If Steve "returns" a Stone to one of these timelines, he's not really "returning" it, just creating a new timeline where he has put it back, while the timeline where he hasn't continues to exist.

So - under the directors' interpretation of the

time travel, why do Steve/the Avengers care about returning the Stones when doing so will just create more branched timelines rather than "fixing" the timelines they've previously created?

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    Are the spoiler tags really necessary? It's important to keep the title spoiler free, but once you click the question aren't you asking to see things about Endgame? May 8, 2019 at 20:39
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    @user1717828 I think I recall some policy about spoilertext in the bit of the question that can be seen from the front page? Then I just did the whole question for consistency. Not sure what this community's policy is on spoilers though, happy to follow direction.
    – Vigil
    May 8, 2019 at 22:12
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    Also you might add: if all of Steve's visits to the past create branching timelines, why does old Steve show up on the park bench in this timeline?
    – workerjoe
    May 9, 2019 at 0:07
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    It's less an issue of having text protected by spoiler tags, and more that you decided to create a bunch of separate spoiler tags instead of one or two. There's no need to drop out of a spoiler just to include half a sentence that only makes sense when in context of that spoiler ;)
    – Mwr247
    May 9, 2019 at 4:18
  • Dear Nathan Cooper, please do not edit posts to be an entire spoiler block as that makes it illegible...
    – Edlothiad
    May 9, 2019 at 12:13

5 Answers 5


Disclaimer: Ever since seeing the film I have been firmly on the interpretation that the writer's explanation is correct and I never believed the Russos' interpretation. As such my answer will be biased that way.

I think this is mainly down to the fact that in universe they believe this to be the correct action to return the timelines back to normal per Professor Hulk's and the Ancient One's conversation.

The Ancient One: The Infinity Stones create what you experience as the flow of time. Remove one of the stones, and that flow splits. Now this may benefit your reality. But my new one, not so much. In this new branched reality, without our chief weapon against the forces of darkness, our world will be overrun. Millions will suffer. So, tell me, doctor, can your science prevent all that?

Professor Hulk: No. But we can erase it. Because once we're done with the stones, we can return each one into its own timeline at the moment it was taken. So, chronologically... In that reality.... it never left.

Avengers: Endgame

Whatever the directors' or writers' interpretation doesn't matter because in universe this is what they believed they needed to do.

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    Though the Ancient One's statement doesn't make a lot of sense, given that the world wasn't overrun after Thanos reduced them to atoms. (As mentioned by others, e.g. in the "Life without Infinity Stones" section here.)
    – Jacob C.
    May 8, 2019 at 19:22
  • Eh, OTOH, I guess this address that, kinda.
    – Jacob C.
    May 8, 2019 at 19:24
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    @JacobC.if you think about it, stealing the Time Stone in 2012 would've meant that Dr. Strange wouldn't have saved the world during the events of his movie. That's what I think the Ancient One was referring to. Presumably the Earth is in danger of being overrun after the Time Stone is destroyed, but we'll have to wait until Dr. Strange 2 to see how they deal with it. May 8, 2019 at 19:48
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    @JacobC.the "dark" forces might not exactly know that the stone is gone, but they might attack at some point - as DaaaahWhoosh points out, Dormammu certainly does later in Strange's movie, but others might be out there as well. We might see about how well they can detect this reduction in power on Earth in the next Strange movie - if they don't choose to push this under the rug. May 8, 2019 at 19:58
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    @JacobC. he only reduced them to atoms, he didn't remove them from the timeline. They still exist, just not in any useful form.
    – OrangeDog
    May 9, 2019 at 19:31

Captain America did not create new timeline branches when he time-traveled to 1970, 2014, 2015, and 2016 to return the Infinity Stones. He was instead revisiting the same timelines that had already been created by the Time Heist.

We know it is possible to "dial up" and revisit a particular time branch once it has been created, because Thanos does this in 2014 to follow the Avengers back to Earth in 2023. Thanos does not arrive in a 2023 where he disappeared mysteriously nine years earlier (the way that Scott Lang time-traveled to a future in which he was presumed to be dead). Rather, Thanos enters a timeline where there had already existed another version of himself who used the Infinity Gauntlet in 2018 and was then beheaded by Stormbreaker.

What Steve Rogers does at the end of Endgame is dial up the four timelines the Avengers created and pop in at precisely the moment when each stone was removed from the timeline. There is no possibility of him interacting with the Time Heist teams because he is appearing at the very moment they leave. It then does not matter if Steve leaves after taking a couple breaths of air or hangs around Asgard for a couple of years, goes and rescues Bucky, etc. No matter how much he alters history, it is still just one timeline and he has not created any branches that will be left without one of the Infinity Stones.

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    Yet somehow staying behind in the branched timeline caused him to appear in the "prime" timeline as an old man. That seems like causing a change in the past, ended up changing the future in that same line, instead of creating a new branch. May 9, 2019 at 11:06
  • If you get into a deep freezer or stasis chamber, or even if you just accelerate near C (or spend some time in the quantum realm) and experience time dilation, that isn't time travel. May 9, 2019 at 12:51
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    @Bradley Uffner Yes-- under this interpretation, Steve staying in the past would create a new branch of the timeline, which is why I favor the Russos' explanation that Steve lived his life in another timeline and found some means of returning to the "main" branch of the timeline after he became Old Cap. Note that in this case, the branch that Steve created by remaining in the past was not missing any Infinity Stones and was therefore "safe" according to the Ancient One's warning.
    – Nathan K.
    May 9, 2019 at 13:03
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    I think we have evidence (well, more like a suggestion) of Old Cap coming from another timeline as well, in that he brought an undamaged shield to give to Sam Wilson. It's not conclusive evidence, since there are a number of ways Steve could have had a new shield made. But I like the suggestion that it is the shield, which is possible if it came from an alternate timeline.
    – Nathan K.
    May 9, 2019 at 13:10

I don't think the writers or directors have made definitive statements on exactly what creates an alternate reality.

From the movie itself — specifically, Banner's conversation with the Ancient One, and her handy timeline diagram — we know that the Infinity Stones have to be returned, because leaving a branched timeline without an Infinity Stone would be bad for that timeline.

As such, Steve is presumably travelling to the specific alternate realities that the Stones were taken from, and making sure that those realities have all the Stones in them as they should, somehow without creating any new alternate realities (or at least any new alternate realities with missing Stones).

(Unless, of course, he messes something up, and creates bad alternate realities to be explored in future movies/comics/Disney Plus shows.)

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    @HRIATEXP The current timeline has the stones, they were just reduced to their atoms by Thanos.
    – TheLethalCarrot
    May 8, 2019 at 16:04
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    @HRIATEXP: the current timeline was already without any stones for five years after Thanos destroyed them. That, apparently, is fine. May 8, 2019 at 16:05
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    I don't think this answer addresses (either by explanation or frame-challenge) the assertion that since "returning" to these specific timelines is affecting the past and thus creates a new branch (just like the directors asserted Steve did in the Steve&Peggy timeline) the end result of these return trips would just be an increase in the number of branched timelines (with all the new ones having 6 infinity stones), rather than resulting in "fixing" the "original" branches without infinity stones.
    – Vigil
    May 8, 2019 at 16:10
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    @Dave: I don't think that's what the movie is telling us. Returning the stones doesn't, for example, prevent future Nebula's memories from being stolen by past-Nebula, or prevent Loki from escaping New York in 2012 with the Time Stone. My best guess was that the act of time travel itself creates an alternative reality (“their past becomes your future”), but clearly Steve's travel back to replace the Stones somehow doesn't create another alternate reality. Ultimately, it's time travel, and its not Primer, so it's not going to make much sense. You gotta let it go. May 8, 2019 at 16:13
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    @Vigil: the movie really seems to be telling us that returning the Stones does not create a new branch; rather it prevents a Stone-less branch existing. That's what Banner says to the Ancient One, and she doesn't contradict him. May 8, 2019 at 16:14

The Ancient One phrased it this way:

The Infinity Stones create what you experience as the flow of time. Remove one of the stones, and that flow splits. Now this may benefit your reality. But my new one, not so much. In this new branched reality, without our chief weapon against the forces of darkness, our world will be overrun.

Note, it's not just the absence of the Infinity Stone that is the problem - it's that with it gone, it can't be used. Several of the Stones are in places where they cannot or will not be used, but the Time Stone in particular is held ready for use whenever it is needed. Not having it means that an enemy that would have been defeated would instead triumph. For example, if the Ancient One gives up the Stone, then Doctor Strange could never have used it to defeat Dormamu, with terrible consequences for Earth, and indeed our entire reality.

As long as the Stones are put back where - and when - they were taken from, then anyone who was subsequently going to use them can still do so, and history can still proceed as it would have.

  • I think you misunderstood the question, the problem is that presumably bringing back the infinity stones would just branch timelines again and so there are still just as many timelines left without infinity stones. May 9, 2019 at 21:53

The two viewpoints aren't necessarily in conflict, as long as the actions of the time travelers is not incompatible with events (not creating a contradiction).

And they did a very, very good job with continuity in this film. It's obvious a lot of fact-checkers spent a lot of bleary nights going through each past movie with a notepad.

The Hulk-bump and extra Iron Man caused Loki to escape with the Tesseract? Nothing in The Avengers movie supported that, true... but nothing contradicts it either. For all we know, that's what happened the first time and the Avengers movie just didn't show it. (it would be exactly the kind of thing that happens in the MCU, wouldn't it?) The writers carefully built this kind of "plausible deniability" into the film.

And again - Agent Carter quietly hooking up with Captain America'2023 in 1948, keeping the relationship a secret from the world, even to Cap'14 -- that's plausible too. Carter is certainly capable of it.

The only glaring timeline-breaker is Thanos'14 coming to 2023 and getting destroyed by the Stark-Snap, meaning his existence ends as of 2014, he never pursues the Infinity Stones, never decimates Asgardians, and never does the snap in the first place. Meaning the Avengers are not motivated to un-snap, and never bother exploring time travel in the first place. Total paradox.

But hold on -- what did the Stark-Snap actually do? We don't know. The movie doesn't say. But we already learned Snaps don't irrevocably destroy people since they were able to Snap them back. If the snap actually sent them back to 2014 where they belonged (either because of Stark's holding the intention, or just because that's how Nature made it work), then even that paradox would be repaired. Would it have wiped their memories of the discovery of second Nebula onward? Probably ... or would Thanos, being so powerful, still have "felt" something was up? Maybe that's the tipping point that made him say "Fine. I'll do it myself."

Of course, that still leaves the puzzle of Nebula being both dead and not-dead. Maybe the Stark-Snap restored and sent back everyone, even the dead, even the wrecked starship.

I think they could have settled (belabored?) these points in the movie narratively. But you have to admit, leaving us these things to discuss does make the movie series more interesting.

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    Your claim that "nothing contradicts" Loki escaping with the tesseract in the first Avengers movie is wrong. We got a clear scene of the Avengers taking the tesseract out of its suitcase and giving it to Thor, who used it to teleport himself and Loki (still in restraints) back to Asgard. See youtube.com/watch?v=kY2PuIaYdtQ&t=43s. Not to mention the complications from Future!Cap telling Past!Cap that Bucky is still alive... And that's just the Space Stone. Nebula and Rhodey grabbing the Power Stone conflicts with the entire plot of Guardians of the Galaxy.
    – MJ713
    May 9, 2019 at 22:56

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