Time travel is a complicated topic, and to make sure that they got the whole concept a little bit right, Avengers: Endgame writers Stephen McFeely and Christopher Markus decided to consult a quantum physicist. During their session, the physicist told the writers that the time travel in the science fiction classic Back to the Future was nothing but "bullsh*t," a piece of advice which was later on incorporated into a line by Ant-Man (Paul Rudd).
Speaking with fans during Marvel's Endgame panel at the 2019 San Diego Comic-Con International last week (via ComicBook.com), McFeely openly said that "Back to the Future is bullshit" after being asked about what the film's writers learned after consulting with science experts.
"It's a direct quote from a physicist," Markus added.
"What other franchise could do what we were allowed to do? Go back to the other movies to get your six MacGuffins and bring them forward to solve your problem, and allow yourself to do all sorts of emotional triage as you do it — people get to meet their fathers and mothers and whatnot," McFeely went on explaining.
However, the film couldn't operate by the same rules as Back to the Future. In the film series, objects from the past would change the future. Back to the Future Part II has Marty McFly's time travel adventures altering his present-day reality because of what Biff discovers.
"So you can imagine that if every time a new universe was created, we would get nowhere, and we wouldn't know how to solve anyone, because which one did what? It was not helpful to us and we were worried that maybe we couldn't even do this idea," McFeely said.
It's a good thing then that the writers consulted with a physicist. Though we're pretty certain that time travel is much more complicated than how Endgame depicted it.
Avengers: Endgame is now available on Digital HD.