Avengers Endgame Time Travel Explained: Alternate Timelines, Old Captain America, More
“We’re in the endgame now.” Benedict Cumberbatch’s Doctor Strange already hinted toward a possible solution to the Thanos problem in the final act of Avengers: Infinity War, when he sifted through over a million possible futures using the Eye of Agamotto to find only one where the heroes emerged victorious. We predicted that the Sorcerer Supreme had a plan when he willing parted with the Time Stone to save Tony Stark’s life, and it all comes together in Avengers: Endgame.
The aptly named finale of the MCU’s overarching plot finds its way through Strange’s intended future using, you guessed it, time travel, though this rendition of the overused sci-fi movie trope works a little differently than the classic take. In fact, the movie directly references the likes of Back to the Future and Terminator to clarify that time travel works differently in the Marvel Cinematic Universe. In what follows, we attempt to understand the concept and its implications on the plot while answering some of the questions you may have been left with after the credits began to roll.
Spoiler Alert: The following contains major spoilers for Avengers: Endgame.
Here goes nothing.
Time Travel and the Quantum Realm
The heroes leverage a limited supply of Pym Particles to shrink down to subatomic sizes so they may navigate through the Quantum Realm, which, as Michael Douglas’ Hank Pym explains in Ant-Man, is “a reality where all concepts of time and space become irrelevant as you shrink for all eternity.” As Pym’s quantum field generator only allows travel to and from the Quantum Realm with no control over the time aspect, it is left to Tony Stark to develop a way for the team to emerge at specific times in the past and then return to their own. To that end, he provides each member with a personal nav system for the Quantum Realm – a Quantum Realm GPS band, if you will – which also serves as a tether for the quantum field generator, so they may find their way back to their own time.
How Time Travel Works in the Marvel Cinematic Universe
So, why exactly didn’t they go for a simpler strategy, like killing Thanos before he got to the Infinity Stones? Don Cheadle’s War Machine does suggest a similar albeit darker version of the same when he casually muses about assassinating baby Thanos. Simply put, if you travel back in time and change the past, you aren’t really changing your own future as said future in already your past.
Another way to look at it would be that the tiniest change to past events could also change your past self and their experiences, which may make it so that they never have to travel back to the past. If so, wouldn’t the person that traveled to the past cease to exist in the past, present, and future? It’s a good old-fashioned time paradox.
The movie does away with the confusion of a causal loop using alternate timelines. In the MCU, changing the past, say, by removing an Infinity Stone, creates a new reality with its own sequence of events, as the Ancient One expertly explains to the Hulk, complete with a magical visual aid.
The Infinity Stones create what you experience as the flow of time. Remove one of the stones, and that flow splits. Now this may benefit your reality, but my new one, not so much. In this new branch reality, without our chief weapon against the forces of darkness, our world will be overrun, millions would suffer.
Note, that the Ancient One ties branching timelines directly to the Infinity Stones, though that may just be because the explanation was more relevant in the context of her discussion with Banner.
The concept isn’t new by any means – fans of the Stein’s; Gate anime series will instantly find themselves at home with the idea of branching timelines, and that is just one example.
Explaining Captain America Growing Old
Most of the “how” and “when” of Captain America growing old remains unexplained. At the end of the movie, Steve Rogers takes all six infinity stones and Mjolnir back to their respective timelines to maintain their continuity, but instead of coming back to his own time, he decides to stick around to pursue a life of his own, presumably with his old flame Peggie Carter. He ties the knot and grows old with his new partner, but how and exactly when does he return to his timeline or did he somehow grow old in the same reality?
One possibility may be that somewhere along the way, possibly after his partner passes away, he decides to return to his own timeline to give his friends closure and announce his retirement, bringing along a brand new shield, which he then uses to pass the torch to the Falcon, Sam Wilson, who happens the current Captain America in the comics.
If he did, in fact, grow old in his own timeline, this would mean that time travel in the MCU has some wiggle room when it comes to changing the past – as long as no major changes are made, no new timelines will be created. This viewer, however, felt more inclined to believe in time travel that stays true to the butterfly effect – the theory that even the smallest change can contribute to major events down the line.
How Many Timelines Did the Avengers Create?
Going by how the Hulk explains time travel to the team, the Avengers created a new timeline for every jump they made to a specific time period.
- Captain America, Iron Man, Ant-Man, and the Hulk travel to New York during the battle with the Chitauri in 2012 to gather three of the six Infinity Stones.
- After losing the Tesseract to Loki, Captain America and Iron Man then travel to 1970 to borrow the cube from S.H.I.E.L.D.
- Thor and Rocket travel to 2013 Asgard to extract the Reality Stone from Jane Foster.
- Hawkeye, Black Widow, War Machine, and Nebula travel back to 2014 to retrieve the remaining two stones. The team jumps to the planet Morag. Hawkeye and Black Widow take Rocket’s ship to Vormir to find the Soul Stone while War Machine and Nebula stay behind to look for the Power Stone.
That makes a minimum of four branch timelines, though that is assuming that major changes such as removing the Infinity Stones is what causes a split in time. If not, additional timelines should have been created when Captain America traveled to a time of his choice to settle down with Peggie Carter and even when Clint Barton brings back a baseball glove from his own front yard during a test run of the Quantum Realm time machine.
How did Thanos Time-Jump with an Army?
This one, too, relies heavily on the viewers imagination. The Nebula still loyal to her father does open the gates for the invasion using Stark’s Quantum Realm time machine, but that doesn’t explain how an entire army travels to the original timeline without the Pym Particles or time travel suit required to make the jump.
It may be assumed that Thanos took his time planning the invasion, using the many minds at his disposal to replicate Pym’s tech. Once that is done, he sends Nebula to the exact time the Avengers return to their reality, who in turn lets in her father and his fleet.