Avengers: Endgame has left fans scratching their heads in regards to time travel. The simple response to many of the questions seems to be that "the rules are that there are no rules" to some extent. As the story goes, when something in the past is changed as a result of time travel in Avengers: Endgame, a new reality is created which will, in no way, affect the timeline which the Marvel Cinematic Universe follows. In the case of Loki disappearing with the Space Stone, a new timeline was created for a Disney+ series to follow. In the case of Steve Rogers staying to the past, a new timeline was created where he lived happily ever after with Peggy Carter. However, none of these timelines lead into the main timeline of the MCU. If Marvel Studios had known this was the direction which they were headed from day one, it's possible the rules would have been cleaner and Endgame could have been all that much more impressive.
Endgame made it a point to note that Back to the Future's rules of time travel do not apply to the MCU's mythology. Changing the past does not change the future! In fact, there is no perfect comparison to the MCU's time travel rules from any other title. The closest thing seems to be a comparison to the rules set by the TV series LOST, before writers decided to add the new rule of being able to change things or create new timelines.
Had Marvel Studios known where they were going with Endgame from the start (which is near impossible and part of the reason why they have been so successful), the filmmakers could have followed the LOST format of time travel and created a beast so impressive it may never have seen a parallel. Those rules are defined by a theory referred to as "Whatever Happened, Happened." This means that there is no changing of the past. If a character goes back in time, it becomes their future, but it already happened in the timeline from which they came.
In the case of Endgame, the Avengers heroes going back in time to obtain the Infinity Stones would have already happened, just as the returning of those Infinity Stones as the Ancient One demanded. This would mean that although Tony Stark and Steve Rogers were experiencing 1970 at their current age for the first time, it would have been an event permanently etched into history from the timeline in which they left. They simply had not experienced it themselves yet, though Howard Stark would have had the encounter with his fully grown son, all along.
The way this could been applied would have been seeding small Easter eggs into the previous films which would have been tremendously confusing at the time but paid off in dividends for the Infinity Saga's conclusion. For example, Jane Foster would have looked to Thor in The Dark World and said something like, "I had a dream that this raccoon poked me and took the Aether and then Captain America put it back while holding your hammer," and it would've seemed like a one off joke. The audience would've laughed it off and then began to theorize its importance later. Another example would have been someone claiming to see a second Hulk in 2012's The Avengers or Peter Quill getting knocked out before obtaining the Orb containing the Power Stone in 2014's Guardians of the Galaxy, only to wake up and get it anyway.
This, of course, would mean that Loki's new timeline could not have been created without an exception to the Whatever Happened, Happened rule but, certainly, the writers could have come up with a macguffin to make it possible.
It's probably more beneficial that Marvel Studios president Kevin Feige elected to adapt Marvel Cinematic Universe story threads according to what was working and not working. As a result, it's nearly impossible to know not only that Endgame and its story were a possibility when developing 2012's Avengers movie. Plus, to have dedicated the entire universe to the 22nd film in line could have hurt the original product which built the MCU to the successful franchise it has become. Still, it would have been cool to see those payoffs in Endgame with time travel rules which are simple, impressive, and rewarding!7comments
Avengers: Endgame is now playing in theaters.