Back to the Future Part II1989

Doc:
They're taking her home, to your future home! We'll arrive shorty there after, get her out of there and go back to 1985.

Marty McFly:
You mean, I'm going to see where I live? I'm gonna see myself as an old man?

Doc:
No, no, no Marty, that could result in a... Great scott! Jennifer could conceivably encounter her future self! The consequences of that could be disastrous!

Marty McFly:
Doc, what do you mean?

Doc:
I foresee two possibilities. One, coming face to face with herself 30 years older would put her into shock and she would simply pass out. Or two, the encounter could create a time paradox, the results of which could start a chain reaction that wold unravel the very fabric of the space time continuum, and destroy the entire universe! Granted, that's a worse case senario. The destruction might in fact be very localized, limited to our own galaxy.

Marty McFly:
Well that's a relief.