Many are having a hard enough time understanding Avengers: Endgame's time travel rules and logic, and it turns out not even the film's writers and directors agree on how it works. Even though a bulk of Avengers: Endgame's story revolves around time travel, the explanation for how it works really comes down to two scenes in the movie. When the team is first figuring out how they can do it, Hulk explains that they cannot change their own pasts by going back in time. The Ancient One later explains during one of their time travel missions that they must also fix any changes done during their travels (like taking Infinity Stones), otherwise branch realities would be created.
At the very end of Avengers: Endgame, Captain America is chosen to travel through time again and return the Infinity Stones at the exact moment they were taken, guaranteeing that reality would stay the same. His job is to clip all the branches (including returning Mjolnir to 2013 Asgard), but instead of returning to 2023 when the job is finished, he stays in the past to grow old with Peggy Carter. He is seen in 2023 as an old man, and directors Anthony and Joe Russo previously explained that this is because he returned from a branched reality.
Even though this was widely accepted to be the case, many fans also wondered if there was a chance that Cap grew old with Peggy in the main timeline all along. This would go against the Russo brothers' explanation of the events, but it turns out that Avengers: Endgame writers Christopher Markus and Stephen McFeely don't agree with them. As Markus revealed in a Q&A with Fandango, they believe that Steve's actions did not create a new timeline because of the specifics of The Ancient One's explanation.
That is our theory. We are not experts on time travel, but the Ancient One specifically states that when you take an Infinity Stone out of a timeline it creates a new timeline. So Steve going back and just being there would not create a new timeline. So I reject the "Steve is in an alternate reality" theory.
I do believe that there is simply a period in world history from about '48 to now where there are two Steve Rogers. And anyway, for a large chunk of that one of them is frozen in ice. So it's not like they'd be running into each other.
The Russo brothers have a great working relationship with Markus and McFeely and are normally always on the same page when it comes to explaining what happens in their films. That is what makes this differing mindset all the more surprising, and somewhat confusing. The writers do admit that they aren't experts on time travel and that this is just their interpretation, but could it actually make sense for the MCU to have 2023 Steve Rogers around through all the events since around 1948?
Such an explanation would mean that Avengers: Endgame is embracing the linear timeline with time loops explanation of time travel, where you aren't changing the past but enabling something that already did take place. This would potentially allow Steve to live a normal life for the last 80 years of the MCU that we've never seen, making him the husband that Peggy's referred to in the past but never named. This explanation also means that only changes to the Infinity Stones would create branched realities, while returning Mjolnir could be an expansion on this idea, and Cap going to the past doesn't create one because it already happened.
After appearing to have clarity on what Steve's ending in Avengers: Endgame means, we are now back to square one with two competing explanations. Since both the Russo brothers and Markus and McFeely are done with the MCU for the time being, it may be left up to future MCU stories to actually explain what the in-canon explanation is, but the closing of Cap's story still works on an emotional level no matter what is decided.
- Spider-Man: Far From Home (2019) release date: Jul 02, 2019