Does the physics of Marty’s time travel add up?

  • It's an interesting game to play, trying to make sense of something someone made up for the purposes of fictional entertainment. However, it does remind me of this exchange:

        Leonard Hofstadter: 210, and you throw in the Iron Man helmet.
    
        Stuart:             Are you crazy? That helmet's signed by
                            Robert Downey Jr.
    
        Leonard Hofstadter: So?
    
        Stuart:             Okay, if you're gonna question the importance
                            of an actor's signature on a plastic helmet
                            from a movie based on a comic book, then all
                            of our lives have no meaning!
    
    Maybe out lives have no meaning ...