About the end...
 

You're complaining about the 3 Martys, but if the space time continuum is tearing apart like Doc said, it's "logical" that all the timelines are crushing together no? So all the timelines are joined together in one, which is why the continuum is tearing apart. This is not totally illogical for me, but it's really a disaster. What's your point of view?

BTTF doesn't follow the laws of science!? OMG! OMG! Some one hit me in the head with a frying pan, I'm in shock!

Err did I say something wrong? I don't know how to explain what I think.:(

I guess you could argue that since it's the future the rules are loose but the reality is there should only be one future hence why in part II doc returned to 2015 and saw the EXACT same events happening from his first trip. For instance FCB has faded out because his timeline is no more, he shouldn't be able to come back and cause trouble unless his timeline gets restored. My only theory is perhaps each marty comes from a different time; ie. one from 2034, one from 2035, one from 2036 and they all have their different philopophies. Or i guess with rejuvination clinics, they stop aging. Or you could argue that like doc, marty becomes a perpetual time travelller and thus enounters alternate versions of himself so it becomes a regular thing to run into future versions of himself.

Actually I'm not sure if they're from different timeline or years, but at the end, the Punk rock Marty is arguing with the second because the timeline with Jennifer and her 12 children was already erased. That's confusing in fact.

i guess it happened while he was time traveling hence why he remembers it.

So Doc's solution to the universe tearing itself apart becuase of thier meddling is to ignore the problem while they time travel some more?

I think Doc's "catch up to the present" line answers everything. There are three Martys because there are three different time travelers from three different timelines traveling at the same time. The time ripple effect is now confirmed due to the timestream changes in 1931 catching up to Edna's DeLorean causing it to disappear.

So, once time caught up with the Martys, two of the Martys would disappear (or three if all of them are out of the timestream). This is the reason Doc just leaves with 1986 Marty. Since all of the Martys are worried about the timestream, none of them would change the past to endanger 1986 Marty. So Doc and Marty aren't needed there. Time will fix itself.

Yeah, that's what I was thinking.

It wouldnt have needed to be fixed if Doc wasn't screwing around with the universe in the first place. And after Doc and Marty just finished repairing the collossul screwups they caused, the smart thing would be to destroy the time machine. You know, the thing Doc was adovcating throughout the whole series for this very reason?

But what im wondering is how did all the alterfuture Martys get there and A BLUE deloran?

how do biker marty get a black Delok.i.t.t

Oh a Blue DeLorean, what a brainbuster. It couldn't possibly have anything to do with a paint job that Marty got at a later date, no it must have something to do with quantum physics and time travel

Well, Doc DOES mention that the future isn't written...that is to say, at any point in time, while the past is set in stone (unless you change it)...everyone has free will, and the future is therefore indeterminate...travelling into the future brings you into the logical extrapolation of events as they stood in the past at the time of your departure...

And the multiple future Marty's idea isn't totally implausible considering the bizarre logic of BTTF...

Consider, Marty's original plan to erase the FCB timeline...he and FCB Doc were planning to go back to August 25th 1931...had they succeeded in arriving on that date, there would have been 2 Doc's and 2 Marty's present in 1931 Hill Valley...the 2 Marty's would have been the same individual at different points in his personal timeline...but the 2 Doc's would be different versions from different timelines altogether...Lone Pine/Eastwood Doc from the movies, and FCB Doc...it would have been possible for both to co-exist in 1931...

Now imagine if young Emmett saw both these Docs...from his POV, they would both be possible future versions of him (because, from the POV of anyone in 1931, the future isn't written yet)...he can choose to become either of them in the future, or he can choose a different path entirely...

So multiple future versions can very much co-exist when they travel to the past...

^ Awesome explanation

well that helped....not the sarcastic guy below my first post

Ok, this is convincing but here's a question; at the end of BTTF1, What happens when LP Marty disappears in 1985 to go to 1955?

In BTTF2 it is confirmed that there's only one younger Marty back in 1955. So younger TP and LP doesn't co-exist, but what happens? I can think of 3 cases.

1-TP and LP somehow merges to form a slightly different Marty in 1955.
2-TP Marty gets erased so now its LP Marty's job to get his parents back together, with slightly different actions.
3-LP Marty is erased, he disappears in 1985 but never appears in 1955.

The 3rd one is the easiest one for continuum to handle. Because new personality means events in 1955 would be different. So it would be much easier to just get rid of the new one and keep past as it is. Also if it was TP who gets erased in 1955 when LP arrives, it would have to be the case when LP gets back to 1985, TP Marty would be erased again and LP would take his place. Since such things don't happen, we can conclude that it is always the original one who remains. Other selves just follow his steps but disappear in the end.

Also if it is not possible for them to follow the original traveller's steps, they simply disappear at the moment when they should be travelling as original did. This would explain why there isn't a new Marty in 1986 with Doc when he gets the Key. Since he had no reason, he probably got erased at the moment Marty went back to 1931 in EP1. This way past events are preserved and EP1 Marty survives. New Delorean created by this new Doc doesn't disappear according to this rule because what EP1 Marty travelled with was a duplicate, so Doc was able to come back with his Delorean.

So now back to 3 Martys, let's suppose Marty-A is our original here. B and C can't decide to come earlier in their life spans compared to A, because they have to follow A's steps. They also can't decide to come after in their life spans compared to A, because when they reach the exact moment A decided to travel, they would have been erased like new Marty in 1986 did. Finally, they can't come when they reach the exact moment A decided to travel because then, they would succesfully disappear to 1986 in their own timelines but they would never appear in 1986. Instead they would get erased like LP Marty. So it would be A who gets survived.

Hope I managed to explain clearly. What do you guys think about this?

Ending was done for the lulz. Nothing more.

Also about this regarding my previous post. In such case perhaps one of the Docs would get erased. It could be possible that the moment FCB arrives, LP Doc known as Carl Sagan would fade out since he no more exists. Or perhaps FCB would be erased since LP Doc is the original one compared to him and continuum tries to keep past as unaltered as it can. Either way, there would be 2 of the same Marty from different life spans and only one Doc, not 2 with different personalities.

It is possible that they would co-exist. But then it is all thanks to Marty. Normally FCB would never be able to get to the past without a Delorean. So perhaps different personalities can co-exist but there should be another guy who helped them getting there. In this case, who created 3 different Martys? Because normally, B and C should have followed A's steps with slightly different actions but would just get erased in the end.

If this is the case TTG would gain so much hatred. Some fans already kinda hate TTG because they find this game unsatisfying. If they made an ending just for fun, when fans like to explain things in BTTF universe, it would not be fun really.

I don't see why 'Carl Sagan' LP Doc should be erased, just because his alternate self arrives. I think your confusing the TP Marty-LP Marty issue with this.

The case of TP Marty and LP Marty is kinda different. In that case, TP Marty's actions result in the creation of LP Marty, who makes the SAME trip back to 1955 at the PRECISE same moment as TP Marty did. LP Marty's temporal displacement is just the LP version of the original temporal displacement by TP Marty.

Whereas, in the case of LP Doc and FCB Doc, things are different. LP Doc and FCB would have made different time trips leading to their being present simultaneously in 1931. Therefore, they can co-exist. Of course, LP Doc is 'scheduled' to return to 1986 with Marty and be erased in the process.