Following Avengers: Endgame, there’s been a huge amount of discussion about how the movie dealt with time travel. As joked about by the characters, its depiction of altering the past flew in the face of everything we’ve been taught about the concept from the likes of Back to the Future – if you step on a butterfly or break up your parents, the future will change because of it. Not in Endgame, though, which instead went by the rule that any changes to the past will create a new branch of the timeline.
Many people have debated how it all fits together, but the Russos maintain that the way time travel works in the MCU is explained as best it can be in Endgame. In fact, all the jokes at the classic 1980s movie’s expense were the result of reshoots after test screening audiences were confused about how the film dealt with time travel.
“According by the rules of the movie, as stated by the Hulk and by The Ancient One, we go to great pains to tell you that Back to the Future is bullshit,” said Joe Russo.
“If you’re trying to change the rules of time travel in a movie, unless you are super clear and point out that these are not the rules from Back to the Future, people just won’t understand it. We learned about this after three test screenings. We had to go back and add in more jokes about Back to the Future so that people would take our multiverse theory seriously.”
Anthony Russo then summed up the key thing about the argument, saying: “Here’s the most important thing about time travel: It doesn’t exist.”
Employing this method of time travel opens the door to a wide Marvel multiverse of varying timelines, and Joe went on to explain how that works to THR, reiterating how Hulk tells it to the other heroes in Endgame.
“The Hulk says if you’re in the present and you go back to the past, you cannot affect the present because it has already occurred. That now becomes your past. Right? And if you’re [currently] in the past, this is now your present. And anything you do in that time shift would create a multiverse reality. It will create a new future, but it’s not going to affect your past.”
Anthony then added to his earlier point that the plot device is so subjective because everyone’s got their own interpretation of it. “But to be honest, talking about time travel is very similar to talking about god,” he said. “Everyone’s going to have a different understanding of what it is.”
Finally, Joe agreed with his brother, explaining that they hoped to create a consistency to the depiction used within this one film alone.
“At the end of the day, any thinking about time travel breaks down. What we tried to do was make sure the rules we were playing with [in regard to] time travel were honored by the plot of the movie.”
Of course, Steve Rogers’ appearance as an old man in the movie’s final scene causes some wrinkles (pun intended) in Avengers: Endgame‘s rules of time travel, as Cap should be in another timeline. But that’s a discussion for another day.