The One Paradox in Back to the Future that Can’t Be Explained

Back to the Future Theme Week

Any movie with time travel is likely to have a plot hole. That’s because time is an artificial construct that we use to understand cause and effect. But I don’t want to get bogged down in the science of it all. No matter what type of time travel you use, the story will usually feature two types of stories: 1) the closed loop take where whatever came back in time is destined to come back (examples include Terminator and Star Trek IV) or 2) the mutable future where actions can change the timeline (examples include Terminator 2 and Back to the Future). It’s essentially the determinism vs. free will argument, using a sci-fi construct. I’d like to specifically look at Back to the Future and explain how it is clearly the second type of time travel story, thus leaving us with a dangling thread that is never addressed in any of the sequels. Basically, there’s a second Marty McFly out there.

lone pine mall

Marty returns to 1985 to witness the events he experienced a week ago

In the final act of Back to the Future, Marty McFly improvises a way to save his friend Doc Brown. Marty has traveled to 1955 after seeing Doc get gunned down by terrorists in his native 1985. When he can’t get Doc to read his note that explains what happens, Marty decides to return to 1985 ten minutes early. Marty returns to 1985 but the car breaks down and he arrives too late to save Doc but in time to see the events of the beginning of the movie play out, watching a version of himself jump in the Delorean and escape the terrorists by going to 1955. We’re meant to think this closes a loop but I’ll explain why it does not.

leaving jennifer parker on the porch

The original Marty grew up with a loser family, saw original Doc get killed and then travels back in time to when his parents were his age. By interfering with their lives he risks them never getting together and wiping himself out from existing, but ultimately brings them together and returns home. But as we soon learn, Marty has subtly changed the 1985 he returns to. Examples include the Twin Pines Mall now being called the Lone Pines Mall (Marty took out a tree when he traveled back in time) and waking up to successful parents who no longer tolerate Biff’s bullying ways. Also, Doc from 1955 decided to read Marty’s note and it made him wear a bulletproof vest. The world has changed around Marty. We’re later shown and told that this happens in the second movie: Doc and Marty leave Jennifer in an alternate 1985 to fix the past and Doc says everything will change around her (although since they prevent this timeline from happening, it might be more accurate to say everything there is erased from existence). It seems like if you time travel, you retain your memories of your life but everyone else is rewritten.

two doc browns

The point of all that was to explain that the second Marty, the Marty we see at the end of the movie who escapes into the past is not the same Marty. This is a new version. This Marty grew up with successful parents. And when he goes into the 1955 past, there is already the original Marty there. Multiple instances of a person can exist at the same time with time travel. We see two Martys in the second movie, both at the Enchantment Under the Sea dance. Those Martys are only a couple of days apart in age because he travels to 1955 a second time. The point is, the first Marty goes into the past and changes things, ultimately for the better. But when the next Marty goes to the past there is already a Marty there, changing things. And the second Marty would not want to change things by interacting in any way. What are his options? Interfere with his parents and wipe himself out of existence? If he goes to Doc for help, there’s nothing he’d be able to do. Both Martys can’t use the single lightning bolt to power their car and return home. No, that second Marty would grow old in 1955 while the original Marty lives out his life in the improved 1985. The second Marty cannot close the loop because he exists at the same time as the original Marty and therefore cannot repeat the same actions.

marty mcfly 2 is screwed

Marty screwed himself.

  • Pete Pfau


  • MagusDuality

    Yeah, I’ve actually thought about this before. The way I see it there are at least two or three options, some of which can be supported by (and at the same time can clash with) events in the later movies.

    1.) When the ‘new’ Marty goes back in time, he replaces/merges with the Marty that went in time before, since the past at that point is the same space and time (and in THAT Marty’s past timeline, the OG Marty was in the past). In other words, this is before the ‘branch’ that separates Marty’s successful family and Marty’s ‘loser’ family – the Enchantment Under the Sea Dance (or, more specifically, Marty first saving George from getting hit by the car). This can lead to one of two things – if he does the same exact things, it just creates a loop, and we have no issues. If he’s a different Marty with a different mindset (which he doesn’t appear to be, since he’s in the exact same situation with Doc that original Marty was), he might do things differently, causing a new future to be created again. This leads into my second option.

    2.) Based on the ‘Many Worlds’ interpretation of the universe, the new Marty could go back and do something different than OG Marty that we follow in the movies, resulting in another, different future. This creates another timeline where the parents are different, or where maybe he isn’t able to get his parents together, or kills Biff, or something else. Any number of things that could result in far bigger changes to the future. Heck, what if he was with Doc and somehow did something that got Doc killed? He’d be stuck in the 50’s permanently. Or, maybe he does things just right (likely unintentionally) where he ends up making the future end up exactly like it was in OG Marty’s original timeline. What would happen then? Would he freak out and demand Doc let him go back to fix it? Would he leave his loser family and go off with Doc somewhere? Would he just continue on with life but with a new perspective, working to change his family?

    The problem with using the ‘Many Worlds’ interpretation is that BTTF 2 actually aligns with it one minute, then negates it the next minute. Doc’s explanation of the new timeline when Biff has the Almanac is ‘Many Worlds’ logic. However, in the ‘Many Worlds’ interpretation Old Biff wouldn’t have been able to go forward in time to deliver the Delorean back to them. He would end up in the future of the NEW reality he helped create (as Doc actually explains to Marty later on in the movie!). And Jennifer, left in alternate 1985, would still be there, not absorbed into our own.

    See, there would actually be a new Marty, Doc, and Jennifer in each timeline they created. This is implied in BTTF 2 as well. Biff as Marty’s step-dad says Marty is “supposed to be in Switzerland.” Meaning there is likely (based on the rules put upon by this article, and the first movie) another Marty who actually IS in Switzerland, unaware of anything happening here. He is the Marty of the timeline where Biff got the Almanac. Also meaning the Doc of that timeline is in an insane asylum, as he shows Marty. What this means is that ANY time they change the past, they’re creating a new timeline. Meaning that at the end of BTTF 2 there should be a new Marty, Jennifer, and Doc in their 1985 world (which is effectively the same as the timeline at the end of BTTF 1, but not the same – the past of BTTF 1 did not have the Almanac). AND it means there should be another version of Marty and Doc at the end of BTTF 3 as well, because technically it’s another timeline, just one that diverged much earlier (1885 instead of 1955).

    3.) The “Double Loop” theory. Take the concept that the Marty that goes back in time (Marty Prime, I guess, not OG Marty) causes stuff that ends up exactly like OG Marty’s past. If that occurs, he will also get back to 1985, possibly the same way (10 minutes before he left). He would witness what is basically the equivalent of OG Marty go back in time, just to cause what we see in BTTF 1 again. Thus we would loop in what would basically be a figure 8. Well, more like an infinity symbol with a line going out of each end. A tied ribbon, maybe, with hanging loose ends.

    All of these assume that Marty just overwrites the Marty that went back previously, when he goes back. If he doesn’t (and I’m not sure how he could, seeing as he travels back to the exact same second and space each time), he’d have to team up with the Marty there. If that kept going either one Marty would have to kill the other, one would have to stay or leave in 1985, or both would go back to the future. But if that keeps looping… going to be lots of Marty’s if this isn’t the ‘Many Worlds’ version.

    Well, I didn’t mean to write a dissertation, but yeah.

  • Skewed_View

    It’s really going to suck when second Marty gets back to 1955, and doesn’t know that there is anything that he needs to fix, because his life is great. So all he does is spend his time with Doc Brown working on the plan to get back to 1985. Even if he sees things not going very well for his parents, he won’t intervene because he has no reason to think things won’t work out.
    Then second Marty gets back to 1985, and he now has first Marty’s crappy family, and can’t figure out what happened.

  • MagusDuality

    Well, Marty didn’t intentionally try to fix his parents in BTTF, it just kindof turned out that way from him messing things up accidentally and then having to correct things. I agree with you about the new universe creation, that’s kindof what I was talking about. Marty Prime going back would create another universe, and so on and so forth.

  • Wow thanks for the input!

  • Chris Piers

    So in Skewed_View’s interpretation, every time Marty goes back he’s creating a new timeline that basically swaps back and forth infinitely? That sounds valid. The one issue I can think of is that in Back to the Future II, Doc and Marty go to 1955 again and the Marty from the first movie is there. I think when Doc draws the branching timeline on the chalkboard in the second movie, that’s not quite how the movie treats things. They show time overwriting one timeline, not creating parallel branches.

  • Chris Piers

    I appreciate the thought you put into the reply! While the point of the movie was to create a construct that allowed our protagonist to meet his parents at the same age, and not necessarily hold up to intense scrutiny, time travel conundrums are fascinating to work out. As far as we know, time travel isn’t possible so ultimately, any rules we create are an interpretation of cause and effect. Which is a fun challenge.

  • MagusDuality

    Well, yes about the back and forth timelines, that’s what I meant in my post about the ‘figure 8’ but with ends hanging off (representing the continuation of BTTF 2 and 3, and the continuation of the ‘other’ Marty that OG Marty saw at the end of BTTF 1.

    But yeah, the movies kind of break down a bit depending on what you’re looking at, but mostly they just show some sort of ‘delayed’ overwriting of the original timeline. That explains how Old Biff is able to go forward to get the Delorean back to Doc and Marty, but Doc and Marty can’t go forward from the altered 1985:

    Marty: “Okay, so we go back to the future, and we stop old Biff from bringing the-”
    Doc: “We can’t – because if we travel into the future from this point in time then we will end up in the future of this reality.”

    Maybe the only explanation in this instance is that changes to the timeline create ‘waves’ in the timeline, that don’t instantaneously change the future, but echo out and gradually re-fit the timeline. Maybe Old Biff just got out ahead of the wave. I think that’s actually the idea the writers went with, but I’m not sure.

  • MagusDuality

    Oh definitely – in the end it’s just a mind-bending look at ‘time travel’ as a narrative instrument rather than a real philosophical statement (unlike, say Primer). But as you say, it’s a fun challenge to try to work out how time travel would affect things, which is why so many books, movies, and video games use it!

  • MagusDuality

    No problem! I wrote a paper on Back to the Future back in college, so I’ve done way too much thinking about all this. Not to mention I love BTTF anyways.

  • Chris Piers

    That’s how I think about it. Waves of change rippling forward.

  • Skewed_View

    Maybe each delorean is anchored to the universe it was created in, and the universes it creates. Each delorean was created in a different universe, so they’re not going to be identical and won’t travel to the same places. When Marty Prime (I like that title) goes back to 1955 in BTTF 2, since he’s in the same delorean it’s the same alternate 1955 that was created in the first movie, so in that instance there really were two Marty Primes at the same time?
    Of course, I’m just making stuff up on the spot trying to get these movies to make sense :)

  • Chris Piers

    Oh, that would work. It keeps the DeLorean at the end of BttF 1 from going to the same time and place as Marty Prime originally went to, which would result in an explosive paradox. Then we end up with the recursive back and forth of Marty’s constantly changing his personal past from nerdy parents to cool parents and back and forth ad infinitum.

  • Skewed_View

    Ugh, not to beat a dead horse, but BBTF 2 is on right now, and for the first time in a long time I’m able to sit and watch it. So, the question that I now have is: How did old future Biff return the delorean after he dropped the almanac off with his younger self in 1955?
    Once the time line was changed, he would only be able to travel to 2015 where he was a millionaire.

  • Chris Piers

    Well, BTTF seems to implement a “ripple” idea to the timestream. Changes aren’t instantaneous. They take time to change. It is introduced in the first movie as Marty’s photo of his siblings slowly disappears. And in an extended cut from BTTF 2, you see Old Biff slowly vanish from the timeline once he returns to 2015. Changes to the timeline are not instantaneous, they can take up to a few days.

  • Skewed_View

    I’ll take it :)

  • James Blvd

    There was always one Marty, The Original Marty (O)Marty, who has a loser family, travels back to 1955. He saves his father, George, and gets hit the car, he gets them back together before any paradox can happen, he never changes much from the original timeline, just his father’s personality, and if you notice, he changed his own personality. He tells George and Lorrain if they have a son, who sets fire to the rug, go easy on him, this must have been some sort of dare in the original timeline, and thus he never got punished and his new personality will be that no one can call him chicken now, which is apparent in the sequals, not in the first. (He was actually scared to audition his band in the first.)
    His parents still got together, they still married, had kids, lived at the same house, they still knew Biff, so the Improved Marty (I)Marty, would still do the same things, be a skateboarder, meet Doc, and travel back in time closing the loop. He would go back in time just like he did, see his dad almost get hit, he gets hit puts them back together.(He is now part of the 1955 history unwittingly causing his improvement, causing the Mall to be Lone Pine Mall ect.).
    (O)Marty returned from 1955 to 1985 he still retains his original personality for now because of the “fading” process, seen in the photograph, news paper ect.) He was shocked to see his family had improved, he had a truck, Biff had changed ect. His personality never changed until he went to 2015 and Griff called him chicken, which if you listen carefully the background music score told the story, the hard thong, was the moment that time faded and (O)Marty retained (I)Marty’s new personality and knew nothing of his ((O)Marty’s previous past), and it’s apparent in the rest of the movies.

    The biggest plot hole was, it was said that when Doc tested the Delorian on Einstien he sent him 1 minute to the future and then clearly said that when Einstien reappeared, and caught up with them that he skipped over that minute to instantly arrive in that moment in time. How did they even travel to 2015 and see theirselves? They should have skipped 30 yrs to instantly appear in 2015. This is the biggest plot hole that even Zemekis said he could not explain, but felt it would’ve been a major let down not to go, since they put the cliffhanger in the first movie. And stated he just left it to personal interpretation.
    The best interpretation, would then be explained by the fading process, if traveling to the future is short(minutes), no fading, if traveling years, (fade process happens slow), which would prove itself giving the (O)Marty personality fade wrote above. Doc did seem quite in a hurry in 2015, this could partly be to return to 1985 before the fade, of them missing 30yrs, caught up and took effect.
    Here is another plot hole, Old 2015 Biff steals the time machine and returns to Nov. 12, 1955, no biggie, Marty returned from that date, it was probally still in the Delorian’s data banks. He gives himself young 1955 Biff the Alamanac, he returns before the previously stated time fade occurs, no problem, but the plot hole is why did he return? If hed stayed in 1955 and waited for the time fade to catch up to him, he would fade from existence, his plan would have succeeded and he’d be rich, with no Marty or Doc to ever stop him?
    The only explanation would be greed. He wanted to be rich in 2015, and did not forsee or did not know about the whole time fading scenerio.