Professor Hulk and The Ancient One do their best to make it clear, but moviegoers may still be coming out of Avengers: Endgame wondering about a key plot point.

How are the heroes able to avoid creating a looping paradox?

Let’s break down of the internal logic of the story …

***Spoilers Below Loki***

Kevin Winter/Getty Images

If Thanos from 2014 gets dusted in the future, then he isn’t around to do The Snap in 2018, right?

But if he’s not around to do The Snap, then the heroes never go on the mission that results in 2014 Thanos’ death — which means he survives and causes The Snap after all.

This is the peril of time travel, the possibility of an endless logic loop, doubling back on itself and undoing itself ad infinitum.

That’s why the plan the Avengers come up with isn’t about rewinding the clock.

Basically, don’t think of it as time travel. It’s dimension hopping.

According to the script by Christopher Markus and Stephen McFeely, you can’t go back in time in your own dimension. If you do, you just end up with older or younger versions of yourself. (That’s what happened to Ant-Man. They pushed time through him.)

Think of it literally as a movie — that’s easy to do, right? It’s a continuum, and you can’t rewind your own film while you’re still moving forward. But — you can hop out of your Blu-ray and into a player spinning another disc and land at any point in that copy of that story.

That’s what the heroes do. To put it another way, they copy and paste reality.

That’s why The Ancient One explains to Bruce Banner that removing the stones basically ruins her own timeline. Why is her DVD existence any better than his DVD existence?

That’s why he promises to return the stones, to cause as little disruption to these other worlds as possible. If they can do that (as Captain American says he does at the end) those branched timelines realign with the central timeline — let’s call it the Prime Timeline — and it’s like the stones never left.

When the three teams jump back in time, they’re really jumping to three other screenings of the movie.

When Thanos 2014 — the Thanos from the time of the first Guardians of the Galaxy movie — gets wind of their plot and travels forward in time to show up above upstate New York five years after the snap, he’s a different Thanos.

He can die there in a cloud of dust without creating a paradox in that timeline because he’s a visitor from another copy of the movie.

However, yes, back in his own Blu-ray, he’s now dead and The Snap never even happens. That remains a branch that can’t realign with the Prime Timeline because it has changed too much.

Loki vanished in the Avengers 2012 timeline when he grabbed the Tesseract, so even though he remains dead in the Prime Timeline, he is free to make mischief in this other branched timeline. (Expect that to be where this character’s upcoming Disney+ series is set.)

The Gamora from 2014 who ventured forward in time with Thanos and her still-evil sister Gamora has ended up trapped in the new timeline, but the Gamora we already know is still dead, sacrificed to the Soul Stone.

Gamora 2014 has no memory of any of the Guardians of the Galaxy experiences, or Peter Quill, or any of it. That Gamora is gone. New Gamora could still be a part of Guardians of the Galaxy Vol. 3. Just expect her to have a significantly different personality.

This is also why Nebula can kill her 2014 self without disappearing. She’s not killing herself from the past, she’s killing a counterpart from another Blu-ray. To draw another metaphor, think of it like Toy Story, when Buzz Lightyear meets another Buzz Lightyear toy. It’s a version of him, yeah, but a different one from the Buzz we know.

Again — that separate 2014 timeline then branches off without Thanos, no Nebula, and also absent Gamora.

When Captain America goes back to return all the borrowed gems, he stays behind not in the past we know, but technically in a different branched reality.

Basically, he goes to live in another copy of the movie.

More on that soon from directors Joe and Anthony Russo….

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