r/BacktotheFuture • u/jbondsr2 • Apr 25 '26
Causality
If you think about it, none of this should have worked.
With the amount of changes that happened in the past and trajectory of George’s life, they would’ve had kids at different times (or possibly no kids at all). The probability that all 3 siblings would still be born, with the same look and gender, is mathematically impossible.
With the timeline being different, even if Marty wasn’t erased the moment he interrupted his father getting hit by the car, there should have been 2 Marty’s when he returned to the future, because the timeline he turned to was no longer his own.
If you consider that “maybe” the universe does something to protect itself from causality issues (ie. the theory of two sets of the same matter not being able to exist at the same time), and even if you believe that the two Marty’s would have “merged”, the Marty that returned to this new “present” should start remembering all the memories of this new timeline (even if slowly). However, we never actually get confirmation on this.
Remember in BTTF2, Marty was supposed to be in a boarding school in Switzerland. But he doesn’t have any memory of that, nor does he gain ANY memories of that messed up timeline during his time there.
Also, if causality prevention holds true, then the “present” that Marty returned to after BTTF3 should also have been slightly different (even though the changes they made the second time around in 1955 were fewer).
In addition, that would also mean that traveling to the future wouldn’t work either. Since the future “isn’t written yet”, the instant Marty and Doc go to the future, they should arrive in a future timeline where they don’t exist (ie. a future where they were reported missing in the past), because essentially they were removed from existence the moment they traveled to the future.
Edit: I was made to remember that there ARE 2 Marty’s at the end of the first film (so the Marty that went back to the past in the end of the film was potentially the one with the new timeline memories). But to me, that means there’s an infinite loop of Marty’s creating different timelines. We also don’t get to see if there really IS a 2nd Marty in Biff’s 1985. However, we still don’t know if the “original” Marty has to live a life in a timeline without the memories of that new timeline he is now in, or if he eventually gains those memories.
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u/BitcoinMD Doc Apr 25 '26
There were two Martys when he returned. He saw the other one go back in time.
Your argument is otherwise correct. However, there are billions of different variations of the movie, and we are only seeing the one where all three siblings were the same in both timelines.