The way I see it, the BackToTheFuturePart2 logic is that moving forward in time you remain in the same 'time-line' or 'time-path', just like you fast-forwarded... where-as traveling back in time necessarily jumps you to an alternate dimension the moment you arrive and start impacting things at any level.

If this logic were strictly adhered to I don't see how you could ever return to your original future once you've gone to the past... you'd always be returning to a new future impacted by the past you just messed with. ... something to think about before cranking that dial back to prehistory!

Yep, definitely a plothole. I only noticed it a a while ago when seeing the movie for perhaps the 20th time...definitely felt like I should've noticed it before...and suddenly you can't not notice it.

If it bugs you too much and since it's time travel, you can always imagine some rules that will make it fit. Examples:

1) Doc and Marty are time travelers and thus isolated from time changes that happen around them. The future that old Biff returns to is actually different, but since they're just standing outside in the street they don't notice it.

2) The future old Biff returns to is the same, because all the events including Marty's retrieval of the Almanac already took place. However, since time is still a straight (but distorted) line to Doc and Marty, they first have to go "back" to the altered present, then go to the past and so on.

3) There are no time lines, it's all parallel universes.

@bamdrew: "If this logic were strictly adhered to I don't see how you could ever return to your original future once you've gone to the past" -- Nice theory, but it's proven wrong in BTTF 1 where Marty didn't return to his original future. He landed in the altered future (where his brother's a lawyer, his father's an author, he has a truck, etc.).

@campionidelmondo: Those are some great thoughts that will help me sleep at night. I like the idea of #2, as it reminds me of Bill and Ted: "Later, I'll travel back to before we got locked in this cage and give myself the key... Now I have the key!"

Glad I'm not the only one who overlooked this gaping hole for so many, many years. That's how you know these movies are really great- they're capable of distracting you by entertaining you so thoroughly.

Side note: I learned in the new special features that the original ending was written so that Marty drove the Delorean into a nuclear bomb test detonation in the desert rather than hitting the lightning cable at precisely 88 mph. (And what are the odds he could hit the cable at the split second the lightning bolt was hitting it? Another quirk that's started bothering me.)

@lucky760: "Nice theory, but it's proven wrong in BTTF 1 where Marty didn't return..."
I'm saying at no point in any BTTF has anyone ever returned to their original future after traveling to the past. They return to an altered future.

I think Doc has a line about 'the future hasn't been written yet', as the norm is to alter the future all the time, but going into the past means altering the future again... and I'm arguing you can't ever return to that first time line in a BTTF universe. ... errr, multi-verse

That awesome Bill and Ted bit! Speaks eloquently to the big conceptual hurdles at the heart of time travel of anything informative to the past.

Bill and Ted could be operating on a 'destiny' time line, where traveling back and forward along the same line is possible, the past and future are set, and free will is an illusion!

"Doc replies that if they returned to 2015, they'd be going forward in the skewed timeline where Biff is a billionaire and has destroyed the world, so it wouldn't work. Hmm. Once Old Biff gave Young Biff the almanac, that changed the future and the timeline that Old Biff was existing on, right? That being the case, why is it that when he returned to 2015 he landed back exactly where he left from?"

Well -- and this might be a bit of a stretch -- maybe it's because when Old Biff travels from 1955 to 2015, Young Biff hadn't actually used the almanac yet. Thus the alteration of the timeline hadn't quite been set into motion yet, as it was still possible at that point that something could happen to prevent Young Biff from using the almanac and changing the future. But by 1985, that version of the future was already well underway, and thus Marty and Doc would only be able to travel to the new future, and not the old one. Plus, as we've seen previously in the series (with the fading photograph), alterations to the timeline occur gradually, and are not instantaneous.

@Sarzy YOU'RE NOT THINKING FOURTH DIMENSIONALLY!!!

Biff can't gradually return to a different future. Just like Doc says when they leave Jenifer behind "The change will be instantaneous!" I'm with Lucky on this one, if the past was modified, Biff should not have been returned to the original timeline, he would have gone to the future where Biff was a millionaire and built a casino in that shitty town.

And I for one think the second movie would have ended well with Doc and Marty sucked into a wormhole of nothingness, leaving no room for the pile of dead cheeseburger meat that was the third film.

>> ^JiggaJonson:

@Sarzy YOU'RE NOT THINKING FOURTH DIMENSIONALLY!!!
Biff can't gradually return to a different future. Just like Doc says when they leave Jenifer behind "The change will be instantaneous!" I'm with Lucky on this one, if the past was modified, Biff should not have been returned to the original timeline, he would have gone to the future where Biff was a millionaire and built a casino in that shitty town.
And I for one think the second movie would have ended well with Doc and Marty sucked into a wormhole of nothingness, leaving no room for the pile of dead cheeseburger meat that was the third film.


Actually, there's a deleted scene on the DVD in which Old Biff, after breaking his cane and stumbling away from the Delorean, gradually disappears. You're supposed to infer that the alternate Biff didn't live to be that old, which made Old Biff disappear -- though that's pretty confusing (which is why they cut the scene).

That supports the fact that certain changes occur gradually, otherwise Old Biff would have disappeared the second he handed Young Biff the almanac.

@JiggaJonson: You've got to be kidding (or nuts). Part 3 was truly a phenomenal flick.

@Sarzy: Great point about him fading away. Although the fading away is defined by the film to occur gradually, the traveling through time and timelines was defined to be instantaneous.

Never mind Part 2 paradoxezez, Future Boy!

Howzabout Part One's odd goofs? Marty returns to the "improved" 1985 but neither of his parents recognize their offspring looks EXACTLY like that guitar-shredding "Calvin Klein".

@quantumushroom: I've considered that many times over the years. More and more over time, I feel that is entirely plausible, as I've forgotten what very close friends from my youth looked like and vice versa.

(This is especially true considering that they only knew him for ~5 days.)

@lucky760 it's not bullshit if I'm stating my opinion. Although I'll concede that the 3rd movie isnt as bad as I touted, it's still my least favorite of the bunch.

@Sarzy you shouldnt use the word "fact" so lightly; remember, we're talking about theoretical cinematic time travel.