In Back to the Future (the original movie), Marty comes back from 1955 10 mins early to prevent Doc from being shot (which he fails at). He then rolls up to the Lone Pine Mall and sees himself hit 88 mph and shoot back to 1955 (again). Marty then carries on with this life as usual. What happens to the Marty that goes back to 1955 at the end of the film?

This obviously is a recursive problem where it would create another timeline and Marty would keep coming back 10 mins early to view another Marty zip back to 1955?

  • That is one way to look at it, the other is that they are both the same Marty. Since each of these alternate universes are identical, both are saying the same thing.
    – DampeS8N
    Commented Feb 25, 2011 at 14:02
  • 16
    @benhowdle89: It depends on your perspective. You are thinking of it as a chain of infinite identical universes, and I'm describing it as one guy overlapping himself in one universe. They two are the same statement. Things that are identical are the same.
    – DampeS8N
    Commented Feb 25, 2011 at 15:43
  • 5
    "Quantum Mechanics gives me a headache"
    – Ryan
    Commented May 23, 2011 at 21:32
  • 3
    "Most people think time is a strict progression of cause and effect. But from a non-linear, non-temporal point of view, time is a big ball of timey-wimey....stuff" - The Doctor
    – Jeff
    Commented Aug 23, 2014 at 13:57
  • 2
    That feeling when I head over to StackExchange with a computer question, only to have "Hot Network Questions" persuade me to visit here, and bang goes my afternoon...! #nostalgia
    – EvilDr
    Commented Jul 27, 2018 at 13:47

16 Answers 16


Picture a string - Marty's movement through space and time. Twist a loop in the middle. For a time, the string parallels itself - that's the time there appeared to be two Marty's at the mall parking lot. Then Marty in the time machine travels back, and Marty on foot continues with life.

Same Marty. Just different points along his personal timeline.

  • 36
    The question is: was Marty there watching Doc's death and his own narrow escape from death at the beginning of the movie? Commented Feb 25, 2011 at 20:51
  • 4
    that comment blows my mind :) Commented Feb 25, 2011 at 21:25
  • 8
    @Raskolnikov Yes. He was.
    – user14952
    Commented Dec 16, 2014 at 19:12
  • 2
    There is only one universe at a time. The ripple effect causes any change in the past to catch up to the preset, so there is only one Marty. He existed in 1985, and for a few minutes, he existed then again. The person Marty saw was't him yet. That person would spend a week in 1955 to become him. Commented Aug 23, 2016 at 13:25
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    Raises question: would the Marty who just arrived from 1955 see the sign as "Lone Pine Mall" while the other Marty sees it as "Twin Pines Mall"? And once other Marty travels to 1955, the ripple effect washes over everyone else and it's officially "Lone Pine Mall"? The other alternative would suppose that other Marty grew up in the altered 1985 (based on mall sign changed, Doc's vest, etc.) and a lot just doesn't make sense with that. Commented Nov 23, 2016 at 17:25

OK, maybe I'll give my two cents about what I think is happening. I can see three theories for now:

  1. History is immutable. Whatever has happened, happened. Whatever will happen, will happen and nothing can be changed. Obviously, this is not the philosophy of BTTF, but just for the sake of argument, I'll detail what this would mean: it would mean that the Marty watching the scene in which he leaves is the exact same Marty as the one who left, save of course a week or so in 1955. It would mean that he was already there watching in the scene in the beginning of the movie. It would also mean that the parents of Marty would still be the same crappy parents they were in the beginning. Since this is not what happens, we can exclude this hypothesis.

  2. History can be changed. This seems to be the way it actually works in the movies. But then, there most likely was no peeping Marty in the first introduction of the Doc death scene. If there was a Marty, it is most likely that this Marty was not the same Marty as the one leaving in the same scene. In the scene later in the movie, it is clear that the two Marties have to be different, since the one leaving has the past with the rich parents, while the one arriving has the past with the poor parents. It makes one wonder what happens to the Marty leaving. Since history has been altered, there's a chance for instance that the ripple effect also alters the command pannel of the Deleorean and makes him travel back not to 1955 but to another date. If he travels back to the same 1955, he will in any case run into poor Marty who was there to set things straight. Anyway, while this seems to coincide with the vision expounded in the movie, it has some weird implications.

  3. Another theory is that of the alternate time lines. But that doesn't fit well with the "history rewrites itself" repeated in the movie. Which is also the reason why the sequels seem even more inconsistent. Also, no ripple effect would be needed in that case. Marty appearing in 1955 would instantly create an alternate future. In this theory, the two Marties would again be different. But the problem of having two Marties run around in the past is weaker because it would just correspond with having yet another alternate universe and could thus not interfere with the first alternate created by the first Marty.

In any case, as far as movie one is concerned, it seems to me that the makers opted for number 2.

(Seeing the story from this angle makes it look like there is material for a scifi version of the prince and the pauper where the rich Marty tries to return back in his own time at the cost of the poor Marty. There could be some fights... with lazor beams... lol...)

  • The really confusing thing about BttF physics is that they allow stable time loops in which history can be changed between the start of the loop and the end of it, which is of course also the start. I have no idea how this works, but then, I have no idea how time travel works, so at least I'm consistent. Unlike these movies. Heh.
    – user867
    Commented Mar 11, 2016 at 3:16
  • Masterly analysis. But lazor -> laser. Commented Mar 16, 2016 at 0:14
  • @Faheem: it was a wilful reference. google.be/… Commented Mar 16, 2016 at 5:21

It's a stable time loop where Doc helps Marty return to the future, reconstructs and reads the note, wears a magical bulletproof vest (that can stop point-blank assault rifle fire), sees Marty go back in time, and Marty runs up to him (having arrived 10 minutes before he left).

The worrying question is what happens to the Marty of 2015 after BTTF2...


It's not a second Marty, it's the same Marty, in a different moment in time -- we are seeing the exact same scene from the beginning of the movie, but from another perspective.

I don't believe it's a recursive problem; I have this theory that there is only one personal present. The Marty that is seeing the scene at the end is the Marty that lives in that present and is watching the past, so in the beginning of the movie, there is not a Marty watching outside our field of vision, as the present at that moment is what we are seeing and that hasn't happened yet.

Anyway, the second paragraph is just a theory of mine that I always wondered (and it would explain why I haven't visited myself from the future (yet))

  • At least, your theory fits with the theory used in the movie, cf. the vanishing of Marty's relatives on the photograph. History rewrites itself. But the movie, or at least the sequels are not always consistently using the same idea. Commented Feb 25, 2011 at 21:53
  • Actually, you contradict yourself, since if we follow the "history is rewriting itself" theory, the two Marty's are really different. The one watching the scene is the one with crappy parents, the one leaving while being watched is the one with rich parents. Makes one wonder if the rich Marty gets back to a future with rich or poor parents after his adventure? Commented Feb 25, 2011 at 21:57
  • @Ras, perhaps the parents switch from poor to rich when Marty 1 goes to 1955, because before there's still the chance of Marty 2 stopping him somehow. Also, changes in the past propagate in a "wave" to the future, thus the slowly vanishing of his brothers and then him. And furthermore, it's not an exact science =)
    – juan
    Commented Feb 25, 2011 at 22:26
  • 12 Monkeys anyone? I think that's a great example of a what @Juan is trying to say here.
    – Ivo Flipse
    Commented Feb 26, 2011 at 5:44
  • 12 Monkey's is an example of a stable time loop, in line with what Jeff is saying. Problem is BTTF can't be a stable time loop since the future has been altered. Commented Feb 26, 2011 at 10:30

There's a lot of discontinuity in the movies, but this part in the movie gets it right. In this part you have to see it as if the past is the future is the past. That which happens in the past would have already happened anyway.

In the rest of the movies see time travel as multiple universes.

A better question would be why Old Biff in BTTF2 returns to the same future he left (returning the car) even though he handed life changing information off to himself in the past.

If it's true that he changed the past, (which is the past that Marty returns to where his dad was dead), then how could Old Biff travel to the unchanged future.

My explanation of the phenomena is that it's possible that we're viewing selected portions of a time travel split in time. That in fact when Old Biff returned to the future he split in two, one returns to the timeline where he's rich, the other returns to the timeline where nothing has changed. However that leaves a problem. If he did split in two, then when he returned to the timeline where he was rich, then there'd be two of him, since the original would have no reason to time-travel because he's rich.

  • Ah, but it is much more complicated than that... Old Biff dies/disappears right away after returning to the future. Which means that not only he manages to return to a timeline that does not exist any more, but he is also affected by events from a different timeline! Which, you have to admit, is truly gross. As explained in the DVD specials, the idea was that in the new timeline, he was supposedly shot by Marty's mother during the 1990s, hence he died "retro-actively".
    – dm.skt
    Commented Feb 25, 2011 at 20:46

He goes back to a 1955 that's identical to the one we saw earlier in the film. It's possible he does everything that we saw Marty prime do back then. Who knows? But that is not the same Marty as we saw during the film. Marty2 grew up with successful parents. He grew up with the nearby mall being Lone Pine Mall instead of Twin Pines Mall.

  • Exactly. His parents are successful because of "Calvin," so it's essential for the time loop to continue. Commented Dec 20, 2011 at 20:56

You are not viewing this four dimensionally :).

Always construct a timeline to solve such problems. Don't view anything as a casual link of events or an ordered sequence of events. All of the events should be viewed as a collection of 4-tuples (x,y,z,t).

All time travels should be a closed loop when viewed like this. He goes back to 1955 and does exactly what he did in the movie (unless someone else goes and disturbs that timeline, quantum mechanics uncertainty ignored of course). The one that comes back to 1985 and sees his other self travel to 1955 will carry on living the future (in which he shall make five more time travels). The one from 1955 will keep coming back and do nothing new in those extra 10 minutes to influence his other self in any way.

If the Marty who comes back to 1985 stops his other self from going back to 1955, he would vanish instantly and the doc. would die, the Lone Pine Mall would again become the Twin Pine Mall and the "original timeline" would be restored (in which his dad would be "gullible" and Biff would be his dad's supervisor etc.) with some exceptions that would arise from the two Matry's interactions. This will lead to him succeeding in going to 1955 because now there is no one to stop him. These two cycles would continue alternately. The closed loop described above would never exist.


It can't be the same Marty, because the first Marty grew up in timeline 1 and the second in timelime 2. So they are different people, and the second Marty, who goes back to 1955, would change all things again and create a new timeline. Either that or he dies instantly, as James McCormack explained.


Presumably Rich Marty would have grown up with a different set of stories his parents told him about how they met. They still kissed for the first time at the Enchantment Under The Sea dance, but there was a mysterious kid called "Calvin Klein" who encouraged George and who vanished soon afterwards. Rich Marty saves his Dad from being hit by the car as before, as an instinctive thing, but then when his mother calls him "Calvin Klein" based on the name on his underpants, he realises he's the "Calvin Klein" who got his parents together, and so sets out to do everything his parents told him about what "Calvin Klein" did, from memory.


One theory I have is that Marty 2 would disappear soon after traveling back to '55 in a similar way to Old Biff in BTTF2. That way there is no possible way for Marty 2 to create yet another timeline. I think this is a likely answer given what we are shown in the movie, though you would think it would be Marty Prime who would disappear rather than Marty 2. I once thought Marty's use of the time machine insulated him from the effects, but that would mean Old Biff shouldn't have disappeared either.


When the second Marty goes back to 1955, he is instantly reverted to the Marty of Twin Pines (the one we've been following throughout the movie). Then once he returns, the ripple effect fuses the two Martys together, giving him two sets of memories: Growing up with an alcoholic mom and growing up with a healthy mom and sci fi writer dad.

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    It would help if you can include quotes from the movies to support this statement.
    – Blackwood
    Commented Aug 22, 2016 at 21:15
  • My fellow fanfiction writers of BTTF agree with the idea above.
    – Chris
    Commented Aug 22, 2016 at 23:13

I think that once Marty 2 was sent into 1955, he was lost in time. He wasn't erased from history, but technically died. He just didn't exist anymore afterward.


Now that I think about it, they might be the same Marty. The reason I believe this is that in the Back to the Future films, they make it clear that there cannot be more than one version of someone, just a different history to them.

When Marty came back to 1985, he saw the version of himself that hadn't gone back in time yet. When the second Marty went back to 1955, he had the mindset of the first Marty. Since Marty was the one that used the Delorean and altered his own history, he now remembers two different versions of his life. Same with Biff. When he went back to 1955 to give himself the sports Almanac, he remembered the poor life that he used to have as well as the new one he gave himself. When he returned back to 2015, he had to wait for the effects of his time travel to have an impact on his future. I think that is the main reason that they cut the scene from BTTF 2 where the old Biff disappears.


Well, I have a theory of my own. When Marty sees himself, it was actually himself that grew up in THAT timeline, with his parents being normal and stuff. The Doc befriends Marty in 1985, (the other Marty) knowing he would have to make a time machine for the original Marty's arrival. And, Doc being the smart man he is, he has told Marty if he doesn't do this experiment it will destroy the space time continuum, and he set the delorean back to a time when the Earth hasn't even existed yet, basically plunging the other Marty to his death while him and the original Marty live happily ever after, the end.

  • Stack Exchange is not for theories, it's a Q and A. Read the tour to get a bettter understanding of SE.
    – bleh
    Commented Dec 28, 2016 at 23:20

Whenever a change to the future is made, a branch timeline is made and it doesn't actually "change" their original timeline.

The Marty we know, let's call him Marty 1, created a new timeline, timeline 2. Evidence of this is when Twin Pines Mall changes to Lone Pines Mall. Timeline 2 [really timeline 3 because of the Pines Mall mentioned earlier, but for the purposes of this comment, and to make it SO MUCH simpler to understand, let's call it timeline 2] was created when he met his parents [got ran over instead of George] and met Doc.

The Marty that Marty 1 sees when he returns to 1985 is Marty 2, a Marty who grew up in this timeline [timeline 2] where similar events occur only this timeline's Doc, Doc 2, is aware of the Libyans and came prepared since he met Marty 1 and read his letter. Marty 1 retains the memory of HIS timeline, timeline 1.

Marty 2 would go back and create a new timeline as well, timeline 3, and witness Marty 3 doing the same and etc. Not a loop, but a continuous cycle.

enter image description here

(Made a mistake in the picture. Where it says "M3 changes the future" I meant to put M2 [Marty 2] since that would make sense. Anyway, moving on.)

Unrelated but people wonder how Old Biff from 2015 was able to return to his timeline if this is the case. The common misconception with BTTF is that time changes INSTANTANEOUSLY, when instead it changes GRADUALLY, at a different rate.

Think of the changes as a ripple effect, like how you throw a rock into a pond and ripples in the water take a while to reach the edge. Old Biff, as soon as he gave the Almanac to his younger self, returned to his time before the ripples of time reached 2015. In Marty and Doc's case, the ripples have already washed over their time and the events are set, unless they change it again.

Of course the changes to the timeline happen at different rates (making it convenient and easy for the screenwriters, lol), but what remains constant with the different rates of change is that it's not instantaneous, but gradual.

The time travelers remain unaffected by time travel since they experienced it themselves. Unless it affects their existence of course. When Old Biff returned to his 2015, he looked labored. There's a deleted scene where he slowly fades away since his time traveling effected his existence.

I hope I was able to clear things up in regards to BTTF.

  • So you're suggesting that the BttF films take place within a multiverse of parallel timelines, rather than a single timeline that overwrites itself when history is altered? If that's the case, then why were Marty1 and his siblings fading from existence as a result of George2 and Lorraine2 not getting romantically involved with one another? If your interpretation is correct, those two would've given birth to Marty2, right? Not Marty1. Commented Feb 23, 2022 at 17:40
  • This requires a REALLY COMPLICATED explanation. This is the inherent problem with time travel movies as they can make things complicated, leaving us to fit the pieces (1/3)
    – Dylan
    Commented Feb 23, 2022 at 18:01
  • It's based on a technicality. Like I mentioned earlier, the changes are like a ripple effect. Because Marty spent enough time in his changed timeline he couldn't return to his original since the ripple washed over his time, Marty 1 BECAME a part [or what I call a "full-part" of this timeline's history. Unlike Old Biff, he's become, what I call, a "semi-part", since he was able to return to HIS 2015. Marty essentially created a paradox where both Marty's can exist at the same time. Allow me to elaborate. (2/3)
    – Dylan
    Commented Feb 23, 2022 at 18:06
  • Events in timeline 2 play out nearly 1:1 as timeline 1, so because of that and the fact he has become a part of this timeline's history, he and Marty 2 are technically both affected. It's as if the timeline can't settle on either Marty being the only one, so either both can exist or none can exist. This is probably confusing and I've probably created a host of other problems, but this is the best explanation I can give while simplifying it. I hope I was able to help. Is there anything else I missed? (3/3)
    – Dylan
    Commented Feb 23, 2022 at 18:06
  • Before we go any further, do you believe this interpretation is what the filmmakers actually intended? Commented Feb 23, 2022 at 18:12

Without Marty intervention, "poor" George meets Lorraine and proceeds to have the "poor" Marty we meet in 1985.

Poor Marty goes back in time, and after a few adventures, gives Poor George the gift of courage, creating Rich George, who begets Rich Marty, who we see at the Lone Pine mall in 1985 as he travels back in time, following the Libyan attack.


At that point, Rich Marty materializes right over Poor Marty as they simultaneously appear in 1955. They both die instantly and the farmer buries the twisted merged wreckage in his field.

Without Marty intervention, "poor" George meets Lorraine and proceeds to have the "poor" Marty we meet in 1985...

  • “Rich Marty materializes right over Poor Marty”. What makes you think they will ever meet each other? They're travelling to different timelines (as explained by Doc Brown in the second movie) Commented Nov 16, 2014 at 3:57
  • @ArturoTorresSánchez The parallel timelines thing had to have been a metaphor, or the ripple effect would have had no reason to exist. Also many of the characters' actions would have been rendered largely meaningless.
    – user867
    Commented Mar 11, 2016 at 3:18
  • @user867, we already know the time travel model for BTTF is flawed, but at least it's consistently so. The ripple effect, while impossible in any of the many proposed time travel theories, always works the same in the movies. Commented Mar 11, 2016 at 3:26
  • @ArturoTorresSánchez Exactly.
    – user867
    Commented Mar 11, 2016 at 3:34

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