Doc: I foresee two possibilities. One, coming face to face with herself 30 years older would put her into shock and she’d simply pass out. Or two, the encounter could create a time paradox, the results of which could cause a chain reaction that would unravel the very fabric of the space time continuum, and destroy the entire universe! Granted, that’s a worse case scenario. The destruction might in fact be very localized, limited to merely our own galaxy.
Marty McFly: Well, that’s a relief.
– Back to the Future Part II
This is one of my favorite scenes in the whole movie. I just love the sheer scale of what could happen and in many ways there is a life lesson to be learned here; whenever there is a scale at which things can go wrong we assume the very worst. It’s human nature. It’s a defence mechanism so that we are as best prepared as we can be for it but look what that worrying does to us – makes us ill, irritable etc.
We could, like Jennifer, just simply pass out and the universe will still be here. As Marty said, “That’s a relief”.