I Back-to-the-Future-versen verkar tidsresenärer i stor utsträckning isoleras från resultaten av sina egna handlingar. Marty har till exempel fortfarande detaljerade minnen om sin familj och deras liv efter att han har ändrat tidslinjen i slutet av BTTF1.
Det står till rätta att allt som saknar en existentiell paradox (där resenären gör att han eller hon upphör att existera) inte skulle skapa en direkt paradox. Docen skulle fortfarande komma ihåg varför han hade stört Martys barns liv, även om hans handlingar hade tagit bort den ursprungliga orsaken till hans meddling.
BTTF2 Novelisation visar över denna inkonsekvens med en mästerlig handvåg. Marty finner det hela förvirrande och det ska vi också. Försök att inte tänka på det för hårt.
Doc pulled out his binocular card to get a better look at the courthouse, and what looked to Marty like a robot, with a USA Today logo on its back, taking a picture of the wreckage. Marty realised that very photo must be the one that appeared in the new version of tomorrow’s newspaper - the version they had right in front of them. But that was weird. How could something change when it hadn’t happened yet? Marty decided he still didn’t understand this time travel business at all!
Doc tucked the binocular card back in his pocket and grinned broadly.
‘Proof beyond positive that we’ve succeeded!’ he cheered. ‘Because this hoverboard incident has now occurred, Griff now goes to jail. Therefore, your son won’t go with him tonight, and that robbery will never take place! Thus, due to the ripple effect, the newspaper is now altered!’
‘The ripple effect?’ Marty asked.
Doc nodded. ‘Just as the past affects the future, the future reverberates into the past.’
Whoa. This was heavy. But Marty remembered something like this happening once before, when he had first messed things up in 1955.
‘Kind of like that picture of me and Dave and Linda,’ he asked, ‘where my brother and sister started to disappear?’
‘Precisely!’ Doc patted his young cohort enthusiastically on the shoulder. ‘Marty, we’ve succeeded! Not exactly as I planned, but no matter. Mission accomplished!' He took a step toward the alley. ‘Let’s get Jennifer and go home.’
Officiella BTTF FAQ erbjuder också följande (mindre hjälpsam) info. Det är säkert möjligt att Doc alltid meddled i den händelsen, det är bara att han hade glömt det.
There's a theory (we like to call it the "Self-Preservation Instinct of the Space-Time Continuum Theory") that says that the continuum is always trying to keep itself "on course," and when things happen to change it, it always tries to correct itself. It is much like a river, which tries to keep its overall course. Although earthquakes, fallen trees, floods, or other circumstances might disrupt it at points, the river would cut a new channel so that it would end up back at the same place. Thus, the overall physics (or metaphysics) of the space-time continuum would insure that any of Doc's memories of events that might create paradoxes would become hazy — or be erased.