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Quantum Realm-ish – Time Travel in Avengers: Endgame

” So Back to the Future is a bunch of bullshit?”

-Scott Lang, Avengers: Endgame (2019)

Yeah, spoilers here.

Okay, if you haven’t seen Endgame at this point why are you even here?  Go watch it.



Avengers: Endgame isn’t really any better with its time travel nonsense than Back to the Future (specifically BTTF II).

Yeah, yeah, it does some things right.  At the end of the day though, it’s the same sort of handwavy shenanigans that Back to the Future glosses over.

First, let’s break it down.  What is the problem with Back to the Future as examined by the movie?  It’s the fact that if you go back into the past and change time, you can go ‘back to the future’ to your own timeline.  In fact, if you change the past, you will create another reality entirely, meaning “your past becomes your future,” as Hulk says in the film.  This is a valid criticism, one that Back to the Future doesn’t entirely ignore, but simply addresses when convenient.  It becomes relevant in Back to the Future Part II, but is largely ignored in parts I and III, with changes on the past instead seeming to alter or erase the future/present as the characters know it.  Back to the Future Part II kindof goes back and forth on this, in one turn creating alternate timelines, in another showing singular timelines changed.  So Scott Lang is right that the movie’s logic is nonsensical.  So what’s the problem?


Let’s simplify things a bit.

The problem with Back to the Future, according to Endgame, is:

Changing the past creates alternate timelines, branching rather than overwriting the present/future.  Or as Banner/Hulk says it, “If you travel to the past, that past is your future and your former present becomes the past, which can’t now be changed by your new future.”

This problem comes up all over Back to the Future.  Marty goes back and changes his young parents lives, making his present parents change to more successful, more attractive versions of themselves.  In Back to the Future II Old Biff in 2015 (the future, lol) brings the Gray’s Sports Almanac back to his 1955 self in an effort to make his own life better (ignoring the deleted scene where Old Biff vanishes entirely after he gets back to 2015).  Honestly, Back to the Future III can almost be forgiven, since the timescale is much larger and the changes to the present (1985) are minuscule.

So the big problem can be summarized as this: You can’t influence your present or future by changing the past.  Changing the past creates a new timeline that branches off and creates its own future, meaning your ‘present’ you originated from essentially no longer exists, or is in another, separate timeline.  Funny enough, Back to the Future II actually sortof did this right – Marty and Doc arrive in an altered 1985, twisted based on the actions of Biff in the past.  It clashes with the rest of the movie and the other two films with this logic, but you can read my full thoughts on that time-travel nonsense in one of my other posts.

Endgame essentially sets us up with the same problem – the heroes need to get the past versions of the Infinity Stones to bring back those who were snapped away by Thanos.  Thanos actually “used the Stones to destroy the Stones,” meaning they no longer naturally exist in the Avengers time.  So they need to retrieve them from the past and bring them to the present to correct the problem.

“Wait,” I hear you saying, “Isn’t that exactly the sort of scenario that WOULDN’T work, based on what you were saying earlier?”  Yes, yes it is.

Somehow Avengers: Endgame gets a pass (I guess because it’s otherwise still an incredible film – and hey, Back to the Future is still great as well).  By using the magic science of Pym Particles and the Quantum Realm, apparently the Avengers can not only travel to the past to retrieve the Stones, but they can also travel back to their original present.  This means that the Avengers change the past, creating new timelines where the Stones no longer exist, but are regardless able to return to their own present time – literally meaning Hulk’s earlier statement about “your former present becomes the past” actually holds no weight.  Hilariously, Doc Brown himself would argue that this isn’t possible, as he mentions in Back to the Future Part II.  

Doc: “Obviously… the Time Continuum has been disrupted creating this new temporal event sequence resulting in this alternate reality…”

Marty: “English, Doc!”

Doc: “Prior to this point in time [1985], somewhere in the past the timeline skewed into this tangent creating an alternate 1985…”

Marty: “Right so we go back to the future… and we stop Biff from stealing the Time Machine -“

Doc: “We can’t – because – if we travel into the future from this point in time it will be the future of this reality!”

So, I guess it’s just Pym Particle shenanigans that allow the Avengers to return to their original timeline?  Like I said, handwavy nonsense.

The resolution to this nonsense is the exact same as Back to the Future Part II as well.  The Avengers plan to return each of the Stones back to their original realities, so that events will line up as normal and not create new realities (minus the few screwed up by Loki nabbing the Tesseract and Thanos jumping forward in time).  Back to the Future II uses the same logic about preventing the bad timeline – just get the Gray’s Sports Almanac from young Biff in 1955 and everything goes right back to normal.

The problem with both of these scenarios is one thing: the Butterfly Effect.  No, not the movie, that one is nonsense too (sometimes it makes interesting points, but still picks and chooses when it follows logic).  No, this is the real problem of a small change eventually having much more widespread, potentially unforseen consequences.  Any singular change in time can cause this, not just something as significant as nabbing an Infinity Stone out of S.H.I.E.L.D.’s underground bunker.  One might walk in front of someone, causing them to stop, then they’re just slightly too late for the elevator in their office, meaning they don’t quite get to a meeting on time, which might be the last straw and they get fired – then maybe this spirals into its own chain of events that causes issues for their entire family!  Or maybe, going back further, you prevent two people from meeting just by the simple thing of walking between them at a point where their eyes might have met, meaning they don’t meet and fall in love, and their descendants aren’t ever born!  Or you prevent someone from being hit by a car, when they might have otherwise (in the normal chain of events) have died, meaning they live on and change lives for the better or worse!  ANY change in the past can cause a new branch in time, not just randomly ‘significant’ events like knocking out Starlord and stealing a magical Orb macguffin.

All this isn’t to say Avengers: Endgame is bad because it fudges time travel logic.  Most movies do that, at least to a degree.  I can probably only think of a few movies that have gotten close to correct.  Maybe Pym Particles are just magic, and the ‘Quantum Realm’ travel is less just time travel and more time travel and reality/timeline jumping all in one.  Or maybe it’s just ‘Deus Ex Machina’ for cool plots or whatever.  Makes about as much sense either way.

Still, cool as hell to watch either way.


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