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The 7 Biggest Avengers: Endgame Time-Travel Questions, Answered

Photo: Marvel Studios

Good news: The latest Avengers movie is not confusing at all. It’s a straightforward romance set in a small town, where the superheroes spend the majority of the movie cooking meals, softly bickering, and contemplating the weather. It’s like August: Osage County, only this time Benedict Cumberbatch has a beard.

Just kidding! Avengers: Endgame isn’t the most convoluted time-travel movie of all time, but maybe that’s because we, the audience, were somehow also flung back in time at some point during the course of the movie’s 182 minutes and lost our memories of convoluted time-travel stories along the way. In the 22nd installment to the Marvel Cinematic Universe, there were doppelgänger confrontations, there were conflicting rules about how said doppelgänger confrontations might alter the past or future, there was an ending that made you wonder, Huh, can he do that? In other words, you probably have more than a few lingering questions about how the hell time works in the MCU, and we’re here to answer them:

Massive spoilers ahead for Avengers: Endgame.

What are the rules of time travel according to Bruce Banner?

First, let’s explain why time travel is necessary. The Avengers’ agenda in Endgame is as follows: It’s the year 2023. The Avengers have, by this point, tried and failed to secure the Infinity Stones that Thanos brought with him to his retirement planet after he turned 50 percent of the world to dust. Turns out, in fact, he destroyed the stones, so there’s no way to reverse his deadly snap by simply stealing the rocks back in the current timeline.

Enter Ant-Man, who has finally returned to Avengers headquarters after a conveniently curious rat freed him from the Quantum Realm. He’s back to suggest that the superheroes use his girlfriend’s dad’s technology to — what else? — time travel. Scott was stuck in the microverse for five years, he asserts, but only five hours passed for him. Could his more scientifically inclined colleagues figure out a way to harness the Quantum Realm for the purpose of retrieving the stones? Yes. Tony Stark and Bruce Banner, a.k.a. Professor Hulk, figure it out. How? Not important. (Tony creates, not kidding, GPS bracelets that apparently do all the heavy lifting when it comes to navigating the “everything happened and is happening” nature of the Quantum Realm.) Just know that time is travel possible, and that this is how the Avengers will obtain the stones they need to bring them back to 2023 and correct Thano’s dustup.

Okay, so say we believe the Avengers: Time travel is possible. Fine. How does it work for the people actually traveling through time? What are the consequences of sending groups of superheroes back to various points in history, where they will inevitably encounters loads of familiar faces and alter the course of events as we know them? Well, the answer is both alarmingly simple and achingly complicated. After War Machine asks the gang why they don’t just go back in time and kill Baby Thanos, Banner outlines an early rule for time travel in the Endgame universe: “If you travel back into your own past, that destination becomes your future, and your former present becomes the past, which can’t now be changed by your new future.” If it sounds a little murky, that’s because it is. But the takeaway is: You can’t just kill Baby Thanos, because his death wouldn’t change the snapped timeline the Avengers have already lived; going into the past doesn’t affect their reality, because their reality has already happened. (If you think this sounds a little like a linear timeline, à la the time-travel rules of Harry Potter and the Prisoner of Azkaban, you’re not alone.)

So, okay. That’s why Tony isn’t afraid to speak to his dad in the S.H.I.E.L.D. base in 1970, when he’s attempting to heist the tesseract, or why Captain America isn’t nervous to fight himself in an effort to snag the Space Stone in New York in 2012, or why Thor doesn’t fumble the entire endeavor by crying on his mom’s shoulder the day before she dies. There is no butterfly effect. Endgame basically tries to be like your hippest friend by telling you that everything you’ve ever heard before about time travel before this movie is bogus. “Back to the Future is bullshit!” Ant-Man declares.

What are the rules of time travel according to Tilda Swinton?

Endgame’s easy approach to time travel gets complicated once you start wondering what Tony meant when he mentioned the EPR paradox and the Deutsch proposition, and whipped up that fancy Möbius-strip visual. Deutsch, as in David Deutsch, as in the multiverse? Are we talking about parallel realities?

Yes, we are, which is pretty standard comic-book fare. When Professor Hulk meets the Ancient One in New York in 2012 (we’ll just call her Tilda Swinton from here on out), she sets the team straight: “The Infinity Stones create what you experience as the flow of time,” she tells Banner. “Remove one of the stones and that flow splits.” Here she whips up a handy visual in midair, showing one long, healthy line shooting across the horizon. She mimics plucking a stone from the timeline and a menacing-looking black line branches out from the original. That, she says, is a parallel reality. Welcome to the multiverse.

In conclusion, the Avengers’ meddling might not affect their own timelines, but their actions will amount to new timelines — and, in the case of the stones’ removal, new timelines that lack the cosmic balance of a reality that possess all six stones. Quick on his feet, Banner promises Tilda that the Avengers will return every stone to its own timeline at the very moment it was taken, “so chronologically, in that reality, it never left.” Tilda seems pretty unconvinced, and concerned for all the people who have to live with the consequences of the Avengers’ actions in their branched realities, until Banner tells her that Dr. Strange indirectly approved the plan. And so she tacitly agrees to go along.

The big takeaway from Tilda’s speech is that it allows Endgame to say, “Hey we’re not changing the past, but we might be creating some alternate futures.” But wait: If the stones are cosmically needed to keep the universe in balance, why was it okay for Thanos to destroy them in the first place? The easy answer is: Because the rest of the movie happens.

Did Captain America’s decision to return to the 1940s contradict these rules?

The final scene of Endgame reveals that Steve Rogers (Chris Evans), who was tasked with returning the stones to their respective timelines after the Avengers defeated Thanos, did not instantly return to the present after “trimming the branches.” Instead, he traveled back on his personal timeline, to his superhero point of origin around the time of World War II, and lived out an entire life with Peggy Carter (Hayley Atwell). In the final scene of the movie, we see the two dancing to the song “It’s Been a Long, Long Time,” one of the post popular U.S. pop songs of late 1945, essentially written as an anthem for soldiers returning from WWII. It’s sweet, but does Steve’s little time jaunt totally contradict everything that the movie has established? And what about that TV series Agent Carter? Has its plot been totally undone?

Of all the tim- travel stuff in the movie, Steve’s decision here seems to work with Endgame’s deliberately flexible laws governing time. The simple way to look at it is this: 2023 Steve Rogers is part of a predestination paradox, meaning, he was destined to travel back in time and be quietly reunited with Peggy. Everything in his life prior to returning to the 1940s happened, the only wrinkle being that at certain points there were two Steve Rogers alive on Earth simultaneously. We can call them Young Steve and Old Steve. Young Steve gets frozen in ice before the end of WWII only to wake up in 2012. Old Steve picked up where Young Steve left off, living out a quiet life with the woman of his dreams, approaching old age just as Young Steve wakes up from his chilly nap. As far as Peggy goes, if Steve arrives after 1947, then the events of Agent Carter aren’t impacted at all! The only question left is whether or not the 1970s Peggy we saw in Endgame was already aware of Old Steve, and we’re just going to assume the answer is yes.

Oh, and at certain points in time there were three if not more Steves running around on Earth. In 1970, you’ve got Young Steve in the ice, Time-Traveling Steve with Tony Stark, and Old Steve. Then, in 2012, there’s freshly thawed Young Steve, Time-Traveling Steve, and Old Steve. That’s not even taking into consideration the other Time-Traveling Steves putting Infinity Stones back where they belong, but you get it.

What about the two Nebulas?

Near the end of Endgame, Nebula (Karen Gillan) from 2014 faces Nebula from 2023, which results in the older and wiser Nebula killing the younger hothead Nebula. So what’s the deal with these two Nebulas? Nebulae? Grammatically this situation is about as confusing as it is paradoxically. Your brain wants to believe that as soon as 2023 Nebula shoots 2014 Nebula, that 2023 Nebula should instantly disappear, because that’s what happens in the time-travel movie Looper. If her younger self has been killed by her older self, then how can her older self exist? Wouldn’t this all fall under the grandfather paradox?

According to Professor Hulk’s linear time explanation, no. According to Tilda Swinton’s branch-reality explanation, no. But the movie plays fast and loose with its logic when it comes to the Nebulae. One creative explanation could reference the fact that the memories of the two Nebulas merged thanks to their cybernetic brain implants. If you’ve seen the other franchise Gillan is involved in, Doctor Who, this is kind of like when the Doctor creates an instant “memory” of having already done something through the course of his time travel. If you go back and watch all the various Who episodes in which there are multiple Karen Gillans, it will make Endgame seem straightforward. In any case, Nebula is one of the timey-wimey-est Avengers.

Is Gamora alive again?

Thanos infamously killed Gamora (Zoe Saldana) so he could get the Soul Stone in Infinity War. But she shows up in Endgame as a 2014 version (still bad, not yet in love with Star Lord) of herself, who ends up helping the Avengers defeat a 2014 version (still bad, not yet in possession of the Infinity Stones) of Thanos. This amounts to the reverse of the Nebulae paradox. Gamora from the past has now been put on a different path that seems to prevent her death in her own personal future. But, if future Gamora hadn’t died in Infinity War, then 2014 Gamora couldn’t be given this second chance. Could this have caused a bootstraps paradox or an information paradox? Of all the time-travel paradoxes, this one is the more confusing, and maybe the one most likely to be addressed in a future movie, given that Star Lord (Chris Pratt) was found in an attempt to track Gamora’s whereabouts at the end of Endgame.

It should be noted that the Gamora predicament and the double Nebula problem are both the result of 2014 Thanos getting in on the time-travel game, too. So, if Tony has now snapped him out of existence, it’s possible that the 2014 timeline has branched, and no longer involves Thanos killing Gamora four years later.

What happened to Loki and the tesseract?

Umm, we don’t know. When the contemporary Avengers go back in time to steal the tesseract from themselves and Loki, they manage to screw up so badly that Loki runs away with the tesseract, again. This isn’t readdressed, but it does, maybe, seem to create the most definitive branch timeline. If Loki escapes, and is running around the universe with the tesseract, it could neatly explain why Tom Hiddleston has a Loki TV series booked on Disney+. In terms of explanations within Endgame, there are really only two that don’t involve this being a “mistake.” First, maybe Thor manages to catch up with Loki anyway, and bring him back to Asgard a bit later than expected, causing everything to proceed as close to before as possible. Second, during Captain America’s trip to “trim the branches,” perhaps he returns to this period and “fixes” the error along the way. If that explanation is true, there would be — hold onto your American buttsfour different versions of Steve Rogers alive on Earth in 2012 at the same time.

Wait, can you explain this movie to me using a Back to the Future analogy?

Even though Endgame likes to make fun of Back to the Future, it does borrow directly from the beloved time-travel trilogy in two very specific ways. First, Tilda Swinton’s explanation of the “branches” and her accompanying visual diagram is pretty much exactly like Doc talking about the alternate 1985 in Back to the Future II. The only difference is that in BTTFII, Doc and Marty are trapped in an alternate branch, and in Endgame Tilda is asking Professor Hulk to prevent one of those from forming.

Second, when Captain America shows up as an old man the moment after he disappears to go back in time, this is pretty much exactly like the ending of Back to the Future II and the beginning of Back to the Future III. When Marty sees the DeLorean struck by lighting, a few seconds later some people show up with a letter, perfectly timed to be delivered at that moment. Captain America did the exact same thing at the end of Endgame. The only difference was that he didn’t send a letter. He sent himself. There you go!

7 Biggest Avengers: Endgame Time-Travel Questions, Answered