So how many timelines do we see in the Trilogy?
Guarantee that I will get this wrong, but…
1: The Original 1985 Timeline
The original timeline where Marty’s parents are losers.
Interestingly is in this timeline we see Einstein the dog travel in time 1 minute into the future and we seemingly see him arrive a minute later. We have no evidence if this Einstein could be an alternative Einstein, but as discussed above, it is very possible within the established rules that this could be Einstein arriving on his own unaltered timeline and therefore not create a branch timeline. If it was always Einstein’s destiny to go forwards into the future this doesn’t mean any alternative branches of reality may have been created.
In this reality we are aware that Marty’s parents are losers, and the Doc gets killed by being shot.
2: The Good Timeline
A branch of the original timeline where things change form 1955. Marty stops his parents from having love at first sight and almost stops his siblings and himself from existing. Marty seemingly is able to prevent this becoming a full reality and instead brings his parents together in a way they hadn’t previously become a couple. Upon returning to 1985 we can believe that we now see the future of this timeline and Marty’s parents are successful and the Doc survives.
The future of this timeline is that Marty and Jennifer’s kids get into trouble in 2015 as we learn in BTTF Part 2. When the Doc arrives back from the future at the end of the first film he warns that something has to be done about their kids in the future.
3: The Better Tomorrow Timeline
Marty and Doc save Marty’s kids from legal trouble. As we see in Part 2 Marty and Doc stop Griff from getting Marty Jr involved in criminal activity. We can assume that this puts them onto the straight and narrow. The Doc confirms this from a future newspaper which alters that we see on screen.
3A: The Mysterious Future Timelines
We also learn that Doc may have been to the more distant future to trace back all of the events that lead to Marty and Jennifer’s children getting into trouble. As such it’s impossible to know how many times he may have caused different branches of timelines to form because of his actions.
4: The Powerful Biff Timeline
We see that old Biff goes back in time and enables his younger self to become rich and powerful. This creates what we have referred to as the Powerful Biff timeline.
In this timeline George is killed, Marty is in Switzerland and Doc is committed.
5: The Worst Timeline
We have to assume that Marty and Doc confronting powerful Biff altered the timeline that was in motion and the future of that 1985 would now be different than the destiny where Marty was in Switzerland and Doc was committed. In a grim note you have to believe that Switzerland Marty in particular would have suffered at the hands of powerful Biff.
Also in this timeline, the Good 1985 timeline Jennifer would have been left alone on her porch bench and woke up in a grim world she would have no memory of. With only Einstein the dog from her original timeline also there, Jennifer and Einstein perhaps have the worst fate of anyone.
6: Young Biff Gets the Almanac Timeline But Loses Anyway
When Marty and Doc head back to stop old Biff’s plan to make his younger self rich and powerful we have a large amount of the plot of Part 2. As we see Marty and Doc are able to stop Biff from keeping the Almanac and as a result, as far as we know, this restores the future to be similar to the Good timeline.
This timeline also continues to see Doc get trapped in the past in 1885.
6A: The Good Timeline We Never See
After Marty and Doc stop Biff their plan was to head back to 1985. We can assume this would have restored 1985 to be similar to the Good Timeline, but keep in mind it would now be a fact of the past that Biff met his older self, that he had more run ins with Marty and he crashed his car into a manure truck for a second time. It is also a fact of this timeline that the Doc was killed in 1885.
This 1985 is a continuation of the above timeline but we don’t ever see it on screen to know if this would have played out this way.
7: Marty Saves Doc
In BTTF Part 3 Marty goes back in time to 1885 and saves Doc Brown from Mad Dog Tannen. They also save Clara from going off the edge of Shonash Ravine and therefore save her life. They also hijack a train. All of these things should in theory cause a huge amount of changes for the future.
From this point however Marty is able to go back to 1985 and we see a similar reality to that of the Good Timeline. Again we know this isn’t exactly the same timeline as the Good Timeline as if nothing else Doc and Clara now have a different fate compared to that of what we can otherwise assume they would have had.
Could the fact that depite all of these changes to time 100 years earlier that time was destined to end up roughly in the form of the Good Timeline?
8: Doc Continues to Change the Future
We can’t say for certain how Doc creating a new time machine out of a train would continue to change things, but we do learn that Doc has built a time machine out of a train, had 2 children with Clara, and gone to the future to get the equipment to make the time travelling train be able to fly. All of these things will continue to cause changes to time.
Alterantively…
