Note: This essay was written for the Facebook page of Another Kind of Distance, my time travel podcast with David Fiore. If you want to quibble with our theories or interpretations or offer completely different ones of your own, please comment there or contact us at firstname.lastname@example.org. Our Back to the Future series episode isn't up yet, but this essay may help you get your bearings in our Timecrimes/Primer episode.
EDIT: the epic 3-hour podcast stroll through the BTTF trilogy is now available
EDIT: the epic 3-hour podcast stroll through the BTTF trilogy is now available
I bet when you were ten or eleven or in your early teens, or however old you were when you first saw the Back to the Future series, you followed the movies without any problem and didn't find anything confusing or problematic about the way they handled time travel. That's in stark contrast to Primer, where the time travel is probably internally consistent but the narrative is hellishly confusing. But if you actually lay out the time travel plot in the BTTF series, suddenly it starts sounding just as complicated as the time travel in Primer. And when you then try to figure out how
Ever since Episode 6, The Elements of Time Travel, I've been developing a theory of how narrative perspective relates to the time travel genres that Dave is fond of referring to, and how it can either fix or fuck a time travel narrative. So buckle your seat belts and prepare for a front-seat roller-coaster ride as I describe the time travel plot of the BTTF series; what's wrong with it and how it ought to work (according to how your hosts currently understand time travel narratives); and how thinking about narrative perspective can help make everything clearer.
But only after things get really confusing first. Obviously – spoilers, right?
The Time Travel Plot of Back to the Future
Marty goes back in time and alters the past, creating a Fixed (as in “corrected”) Future.
Marty, Doc, and Jennifer go to the future from the Fixed Future. Future!Future!Biff uses the machine to go back in time, altering the past and therefore changing the future. Then he comes back – although weirdly, nothing has changed yet. There's some kind of delay between changing the past and the changes taking effect?
The original three time travellers go back and find the changed world. Marty and Doc go back in time again, leaving Jennifer in the Alternate Future. They end up in the most recently created past, the one that causes the Fixed Future. Except that F!F!Biff has already been to this past, because it's the past of the timeline that he comes from. (The post-time travel timeline, that is, at the end of the first movie, which goes: Altered Past, Fixed Future, Future Future.) So it's not the Original Altered Past, which we saw in the first movie, but rather the Alternate Future Past, which is the same as the OAP, but with F!F!Biff in it.
Marty intervenes and gets the almanac from F!F!Biff, thereby preventing the Alternate Future. However, when the Doc goes back to what is now again the Fixed Future, he leaves Marty stranded in the altered Alternate Future Past. We are given to understand that the Doc ends up in the Wild West and leaves a letter to be delivered to Marty right after he disappears.
Marty (actually Marty 2) enlists the help of 1955!Doc (who just sent Marty 1 back to the future) to send him to where 1985!Doc is, in the Wild West. Stuff happens in the Wild West with no relevance to time travel, and Marty 2 makes it back to Fixed Future, where he finds Jennifer on the porch where he left her in Alternate Future. Does that seem wrong? Hold that thought.
The timeline is now: Altered Past with Doubly!Thwarted!Biff, Fixed Future – and Future Future. Jennifer has a document from Future Future showing the bad things that we know will happen to Marty as the result of a character flaw. However, based on his experience in the Wild West, he's able to overcome that flaw – and the document changes (in accordance with the rules of this movie). So the final timeline is: Altered Past with Doubly!Thwarted!Biff, Fixed Future, and Fixed Future Future.
Here Come the Problems
How can Future!Future!Biff travel to 1955 then back to the Future Future? In perfectly consistent time travel, from the perspective of Marty and Doc, Biff would disappear forever from their timeline when he went back to 1955 – and they'd also be stranded in the Future Future, because he would have the machine. If we followed Biff's perspective, on the other hand, he would travel back to an Alternate Future Future that follows from the alternate 1985 we saw. And once he's created the Alternate Future,
Marty 1 doesn't time travel in the first place (1985!Doc of this timeline is in an insane asylum), so no Biff would have any reason to worry about Marty 2 coming after him: Marty 2 doesn't exist in this universe.
Imagine, on the other hand, that the Doc builds another time machine so they can go back to 1955 and stop Biff from giving himself the almanac. Now, that doesn't make sense, does it? As soon as Biff has time travelled, he's given himself the almanac: there's no time delay. They should now be in an alternate reality. Except in an alternate reality, they'd be different people or may not even exist. By the movies' logic, maybe their bodies would start disappearing and text would start altering around them.
By strict multiple-timelines logic, on the other hand – F!F!Biff has started his own AU and disappeared permanently from theirs. When they get in the new time machine and go back to 1985, then, it will still be the Fixed Future.
As long as we follow the perspective of one time traveller (or more if they use the same machine at the same time), everything works. When Marty 2 returns to 1985 from his original trip to 1955, he's actually in a new timeline to which he's not native – Marty 1 is. So if he intervened and somehow stopped Marty 1 from going into the past – there would now be two of them in this new timeline. This is the problem faced by the protagonist and the scientist in Timecrimes. Or they think it is – although since that's a loop movie, everything is foreordained anyway. Whereas the problem when Marty 2 watches AU!Marty 1 get into the time machine and go back to 1955 is that BTTF briefly thinks it's a loop movie. In fact, even if this universe's Marty 1 somehow did go back in time at the same moment, in the same way – he would not have been motivated to fix things in 1955, because he already grew up with the fixed family. Which is fine, because he didn't fix his family – Marty 2 did.
Remember: one perspective=one timeline. Marty grew up with the original family. Marty travels into the past – where he meets earlier new-timeline versions of that family that are identical to the original-timeline versions – unless he changes things. Marty (the same Marty, the one we're following!) then goes into the future, where he meets identical new-timeline versions of the family he's altered. If they have a son, and that son is “him,” that son grew up with them, not the original timeline family.
The perspective problem is illustrated again by the events at the end of BTTF 2. When Doc is zapped back to 1885, from his perspective, he arrives in the Wild West, prepares the letter for Marty, and dies. You could film this as consistent time travel by showing him arriving in 1885, then doing a “70 Years Later” ellipsis, where we see Marty watching him disappear and then getting the letter a moment later. Of course that would ruin the pretty awesome timey-wimey, mindy-bendy surprise of how Marty gets the letter, which depends on being limited to his perspective. But the fact is that perspective interruptus occurs throughout the movie.
Perspective and the Two Kinds of Time Travel
In alternate-universe/multiple-timeline time travel, your time-travel is paradox-free because every act of time travel creates a new timeline. That timeline is identical to the one you just left – until you change something. So, at 40 you could travel back to when you're 20 years old. If you never do anything to affect the life of Me 1, Me 1 will grow up to be you and “become” you by time travelling – but “you” in a different timeline. If, on the other hand, you give yourself some stock market tips and then travel back to the future, there will be two versions of you: Me 1, who is rich, and you.
The only thing that's consistent in all of this is you. You keep creating different timelines, and everyone around you is from these alternate timelines, but you are the same self, from the original timeline. Movies start running into trouble with this when there are multiple time travellers and the filmmakers think they can adopt the multiple-character/omniscient perspective of an ordinary movie.
Because multiple-timeline time travel gets enormously confusing, and movies seem to have a haphazard approach to it, I don't think we've seen any clean, consistent example of it, although both Butterfly Effect and the BTTF movies partake of it. Primer might be the cleanest example we've seen, although that didn't make it any clearer.
In “loop”/single-timeline time travel (major examples we've seen: Somewhere in Time, Time Traveller's Wife, Timecrimes), your time travel is paradox-free because everything has already happened the same way. For this, see Time Traveler's Wife and Timecrimes. If at 40 you visit your 20-year-old self, you already have a memory of that visit from the 20-year-old self's perspective. You can't visit your past self bringing new information, because the visit already occurred and you already have all of the information from it.
Although in this type of time travel you have memories of your visits from the earlier self's perspective, what you don't have are memories of people whom you will encounter in your future and their past – when in the future you travel into the past and meet them for the first time from their perspective. They remember your future; and when you do travel back in time, you experience their past.