Markus and McFeely have tirelessly worked on various MCU projects over the years, from all three “Captain America” movies to “Infinity War” and “Endgame.” Speaking to Gothamist about the use of time travel in “Endgame,” the duo explained that this mechanic in the film was necessary to introduce surprise stakes for audiences and followed rules that were in keeping with quantum theories about time travel after they consulted quantum physicists during the filming process. McFeely said:
“We actually brought in two quantum physicists, to ask their opinion about time travel and how if it could be real — how would it work? And both of them said, well, given what we know about particles at the quantum level where new research indicates that the same particle can be in two different places at the same time on the quantum level, that maybe the Quantum Realm established in Ant-Man might allow for some time travel.”
Quantum theory about time travel also leans towards the multi-timeline theory, where the act of traveling forward or backward in time would create a branched reality instead of reversing the canon established in the original timeline. This directly feeds into the multiverse in some sense, especially with how “Loki” treats branched timelines to establish the rules of the Time Variance Authority (TVA). While multiverse jumping is an integral part of the MCU multiverse, branched realities allow fresh stories to gain momentum, as evidenced by Wanda Maximoff’s arc in “Doctor Strange and the Multiverse of Madness.” The duo also clarified that this approach gave rise to “a system that allowed for things to stay the same in [one’s] present reality,” which helped make these major temporal events more digestible for audiences.
