Avengers: Endgame — How time travel works

Marvel Studios’ AVENGERS: ENDGAME..Nebula (Karen Gillan)..Photo: Film Frame..©Marvel Studios 2019

Why the Marvel Cinematic Universe just became a multiverse

Just because the Avengers cannot change their timeline doesn’t mean their actions cannot change the timeline they’re currently in. Turns out the Infinity Stones are what anchor the universe, including time, together. Removing a stone from a certain point in time also creates branching timelines, ones which are also completely unstable.

This is what the Ancient One (Tilda Swinton) warns Hulk about when he tries taking the Time Stone from her. After all, if the Stephen Strange from the alternate 2012 doesn’t have the Time Stone, then his “Dormammu, I’ve come to bargain” plan from Doctor Strange (2016) never happens, and Dormammu wins. Hence why Hulk promises her they’ll return the stones mere moments from which they are taken to “trim the branches.”

Except, as Endgame shows, taking the stones from different realities isn’t the only thing with creates branching timelines. Thanks to the Avengers’ interference, they may have also inadvertently and irrevocably altered the futures of multiple realities regardless of whether they returned the stones or not.

The first divergence occurs in the alternate 2012 timeline. Thanks to the 2012 Hulk running into 2023 Tony Stark, Loki (Tom Hiddleston) escapes with the Tesseract and the Space Stone. Not only does this force Steve and Tony into travelling to 1970 and stealing the Tesseract again, there’s now a universe in which Loki still lives, potentially causing all sorts of mischief. It’s even possible that 2012 Loki gives Thanos the Tesseract even earlier than he did originally. Either way, everything from Avengers on in that timeline no longer happens. At least this explains how Disney Plus can develop a Loki TV streaming series when he’s technically still dead.

Things are even more convoluted when it comes to the alternate 2014 timeline. As 2014 Gamora is now stuck in 2023–where her counterpart is still dead–this means that there’s now a universe in which the Guardians of the Galaxy as we know them never formed. Moreover, because Thanos and his army at the end of the film also come from that alternate timeline, only to be snapped out of existence by Tony Stark, everything from Guardians on–including the events of Infinity War and Endgame–never happens in the alternate 2014 timeline either.

Even when Captain America returns the stones back to the moment from when they’ve been taken, he still changes those timelines. After all, those stones–particularly the 1970 Space Stone, the 2012 Mind Stone, and the 2014 Power Stone–are no longer housed in their original artifacts. Since we didn’t the Tesseract, Loki’s Specter, and the Orb respectively when Steve went back to return the stones, there’s now potentially three more divergent realities in which those artifacts no longer exist.