Bet you thought there was just 1 timeline. Well you’re wrong.

There are no fewer than 21 timelines in the Back to the Future series (although we only ever see 7 of them). But before I break it all down for you, let me explain the 3 Laws of Time Travel.

Law #1: Travelling forward in time causes no adverse effects in your own timeline.

If I were to travel from 2015 and arrive in 2025, the timeline would remain unchanged. I’m simply absent for ten years. Time continues on and the people and the world change during those ten years I was not present. The timeline is unaltered.

Law #2: Travelling back in time always creates an alternate timeline, which is initiated at the point of your arrival.

If I were to travel from 2015 to the year 2005, a new timeline would be created upon my arrival in 2005. My original timeline [2015-A] never had a version of me in its past. So when I arrive in 2005-B, I have created a new timeline by my presence.

Each timeline is like a parallel universe. All events prior to the splintering of the timeline play out identically up to the point where I arrived in the past. From that point in 2005-B, any interactions I may have could cause events to play out differently than they had in my original timeline. They do not, however, actually affect my original timeline [2015-A].

In the case of Marty, his changes are fairly localized to his personal sphere of influence (e.g. his parents meet under different circumstances). But if you were to assassinate the President the changes would become much more widespread and the differences between the two timelines would be much more extreme.

Law #3: Once you have traveled back in time, you can never return to your timeline of origin.

This law is the result of the first two. Law #2 states that travelling backward creates a new timeline, and Law #1 states that travelling forward means you just skip ahead in the timeline you are currently in. Meaning that you can skip ahead as much as you like and stay within your own timeline, but as soon as you go backward you’ll never get home again, you can only move forward in the new timeline or go back and create more new timelines.

Stay with me, we have a long ways to go.

On the surface of the Back to the Future trilogy, it would seem that it all takes place in one timeline; That Marty and Doc are running around trying to put the pieces back in place so that they don’t erase themselves. But what they don’t perceive is that they are actually travelling down a rabbit hole of multiple timelines from which there is no escape. It all starts in…

1985, Timeline-A

Marty-A travels back in time after Doc-A is killed by the Libyans. He arrives in-

1955, Timeline-B

Law #2 of time travel states that since Marty-A is traveling backward he is creating a new timeline at the point of his arrival; November 5th, 1955. And as per Law #3, he cannot return to Timeline-A. So after meddling in the lives of George-B, Lorraine-B and Biff-B, Marty-A works with Doc-B to travel forward to-

1985, Timeline-B

Law #1 of time travel says that you can travel forward and not alter the timeline. When Marty-A jumps forward to 1985 he simply disappears for thirty years and reappears in the same timeline: Timeline-B.

Upon his arrival, Marty-A witnesses Doc-B getting shot down and Marty-B travels back in time to escape the Libyans. What timeline does Marty-B travel to? Who knows!? But thanks to Law #3 he’ll never return to Timeline-B!

Doc-B survives his encounter with the Libyans, thanks to the note that Marty-A wrote him in 1955. But his note didn’t save Doc-A. The version of Dr. Emmett Brown from Marty-A’s original timeline is still dead.

R.I.P. Doc Brown-A

Marty-A then returns home to find his father is now a successful novelist, his mother is thinner, Biff is a car washer and his siblings are successful. The movie makes this seem like all has ended for the better, but in reality Marty-A is a stranger here. Marty-B is gone, so he could theoretically take his place, but he doesn’t have Marty-B’s memories. World events may still be the same, but family he grew up with would be completely different than the one he knew in 1985-A. They would have gone on family vacations that he knows nothing about. He wouldn’t know what they’d gotten him for Christmas last year. He wouldn’t even know where they work. Or for that matter, if and where he himself worked! It’s actually a somewhat terrifying concept; Being a stranger in a mostly familiar world. Everyone you know is changed and all your shared experiences with them are gone. You’re an imposter look-alike pretending to be a you that you’re not.

Not such a happy ending now.

Anyways.

At the end of the first movie, Marty-A and Jennifer-B encounter Doc-Z who whisks them off to a sequel.

Doc-Z? Don’t you mean Doc-B?

It can’t be Doc-B. Yes, he travels to the future of Timeline-B, but when he travels back to get Marty and Jennifer, Doc-B travels to some other timeline that we’ll never know about. But some version of Doc travels back from the future to arrive in Timeline-B. We have no way of knowing what timeline this Doc originated from, but when he traveled back in time he created-

1985, Timeline-C

We don’t spend much time here before Doc-Z, Marty-A and Jennifer-B go to-

2015, Timeline-C

In the fantastic future of hover-boards and flying cars, the gang solves the problem of Marty-Y and Jennifer-X’s delinquent son.

Why is it Marty-Y?

The older version of Marty that we see in BttF2 can’t be Marty-B, because we saw him driving the DeLorean into the past. According to Law #3 of time travel Marty-B can never return to his own timeline due to the changes he’ll cause in the past. And a Marty-C doesn’t exist, because when that timeline was branched off of Timeline-B the only present Marty was Marty-A.

The only explanation is that, much like Doc-Z, Marty-Y is from yet another unseen timeline. His trilogy ended with him in Timeline-B where he and Jennifer-X married and had a transgender daughter and a very stupid son.

Why is she Jennifer-X and not Jennifer-Y?

The older Jennifer we see may actually originate from the same timeline as Marty-Y, in which case she would be Jennifer-Y (and this article should be titled ‘The 20 Timelines of Back to the Future’). But we have no idea of the specifics of her story. Since events tend to play out similarly, her adventure was most likely similar to that of Jennifer-B. In which case it’s safe to assume that she and Marty ended their adventures in Timeline-C but originated from different timelines.

Confused yet? We’re only 6 timelines in.

Back to the story!

From 2015-C, old Biff-C travels back in time to give himself the Gray’s Sports Almanac, which results in-

1955, Timeline-D

This is another timeline we never actually see. But Biff-C hands off the Almanac and, presumably, heads back to 2015.

Law #1 states that Biff-C will remain in timeline-D, so he reappears in 2015 where Biff-D created a vast empire. Although according to the internet, Lorraine-D kills Biff-D in 1996. That means that Biff-C returns to a future where rich Biff-D has been dead for 19 years.

Good luck spending the riches of a corpse, butt-head!

Back in 2015-C we see Old Biff return in the DeLorean, but much like Doc-Z, Marty-Y and Jennifer-X, this can only be a version of Old Biff returning from some other unseen timeline. So as Biff-W stumbles away, Marty-A, Jennifer-B and Doc-Z go back in time to-

1985, Timeline-E

Welcome to Hell Valley, rich Biff’s post-apocalyptic Casino fantasy.

Why don’t they arrive in Timeline-D?

Law #2 of time travelling states that any time you go back you create a new timeline. And in Timeline-D old Biff-C went back to 1955 and then forward again to 2015. In that time, our heroes never appeared and meddled in the events of 1985. But when they do appear they create Timeline-E. Shocked by the world they encounter, Marty-A and Doc-Z decide to return to 1955.

Not before Doc explains Laws #1 and #2 of time travel to Marty (and glossing over the part where they themselves have already created a few alternate timelines).

Now before we jump through time again, lets take a moment to reflect on the shitty fate that befalls Jennifer-B.

Thinking that the timeline will change around her, she’s abandoned in Timeline-E (aka Hell Valley) by Doc-Z and Marty-A as they attempt to re-write history. So let’s recount Jennifer-B’s experience:

Jennifer-B strolls over to her boyfriend’s house where she unknowingly encounters his doppelganger from a parallel timeline.

She gets in a strange car with her doppelganger-boyfriend and a strange old man (also from a parallel universe!) and is whisked away to the future.

Shortly after she arrives in 2015 she’s rendered unconscious!

She awakens in a strange house, and as she attempts to escape she encounters a 47 year old version of herself, the shock of which renders her unconscious again!

When she next awakes, she’s back in 1985 on the porch of a house similar to her own but in a world that has been devastated by the influence of a wealthy and corrupt Biff Tannen.

Not only is the timeline that she is unceremoniously dumped in a ruinous wasteland, but it’s one where her boyfriend is exiled to Switzerland and Doc is locked in an insane asylum. That means that neither Marty-E nor Doc-E ever went travelling through time, and consequently neither did Jennifer-E. Meaning there is already one Jennifer living in the house that Jennifer-B is abandoned at.

Just imagine Jennifer-B waking up groggy and confused. She wanders into what appears to be her home only to discover herself sitting at the kitchen table eating a bowl of Cheerios. After much screaming and fainting, she explains how she came to be here, but no one quite believes her since Doc is a crazy person and no one has heard of Marty. She then has to live out the rest of her life with her doppelganger in the shittiest incarnation of Hill Valley.

Or let’s be serious…they most likely murdered her in a moment of fear and panic, buried her in the backyard and never spoke about it again. It’s Hell Valley…you can get shot for taking a newspaper. Crazy clones from alternate timelines don’t stand much of a chance in Hell Valley.

Shit just got dark.

Either way, Jennifer-B got the shit end of this adventure.

Thinking they’re doing the right thing, and leaving Jennifer-B to a horrible fate, Marty-A and Doc-Z travel to-

1955, Timeline-F

Marty-A and Doc-Z travel back to 1955-F where they attempt to stop Old Biff-V from giving the Almanac to Young Biff-F while trying to avoid running into Marty-U.

Okay I’ll take it slow.

Old Biff-V?

In 2015-C, we see Old Biff-C go back in time and Old Biff-W return. But when Marty-A and Doc-Z arrive in 1955-F they see yet another Old Biff from another timeline. It can’t be Biff-C because he went back in time and returned to a future to live out the life of a rich dead man. It can’t be Old Biff-W because he came from a timeline where Marty-A and Doc-Z hadn’t yet meddled in. So, like Doc-Z, this Old Biff must have come from another unseen timeline.



Marty-U?

Although it would seem that Marty-A is avoiding a past version of himself. But if Law #3 says you can’t return to your original timeline after going back in time, you certainly can’t return to a secondary timeline after leaving it. Since this is Timeline-F, which Marty-A has never been to before, it can’t be Marty-A on stage playing Johnny B. Goode. The events are just playing out in a very similar manner, as they often do.

Since it’s not Marty-A on stage, we have to assume that, like Doc-Z and Old Biff-V, this Marty is also from an unseen timeline, playing out the first part of his adventure in Timeline-F.

After Marty-A and Doc-Z burn the Almanac, the DeLorean is struck by lightning sending Doc-Z to-

1885?, Timeline-G?

We don’t know exactly where Doc-Z ends up, because we never see him again. We know that because of Law #2, he can’t be in Timeline-F, but that’s only assuming that he ended up in the past. While there is a chance that Doc-Z went forward in time within Timeline-F, since there are other versions of Doc (as we’ll soon see) who ended up in 1855 when the DeLorean was struck by lightning, it’s most likely he ended up in the Old West.

Marty-A however receives a letter in-

1955, Timeline-F

-from Doc-T, who was sent back to 1885-F, lived out his life as a blacksmith and was killed by Mad Dog Tannen-F. Marty-A decides to stop this from happening and, with the aid of Doc-F, travels to-

1885, Timeline-H

In the Old West, Marty-A meets Doc-S.

Doc-S?

Unseen timeline, yadda-yadda-yadda.

Anyways, Marty-A works with Doc-S to steal and train. Doc-S rescues Clara-H on the hover-board while Marty-A gets pushed into-

1985, Timeline-H

Shortly after Marty-A’s arrival a train demolishes the DeLorean, so Marty-A seeks out his girlfriend, not realizing that he’s awakening Jennifer-R on the porch swing of her doppelganger’s house.

Jennifer-R?

Much like Jennifer-B who is left to rot in Hell Valley, Jennifer-R was left in a very similar manner but some other set of Marty and Doc. Why they left her is a mystery. Perhaps they were in search of a more illustrious 1985 than this average suburbia.

Together, the two looked on at the wreckage of the DeLorean when-

1985, Timeline-I

A new timeline is spawned around them upon the arrival of Doc-Q, Clara-P and their creepy kids.

Seriously, what’s up with this kid?

Where did Doc-Q and Clara-P come from? Marty-A met Doc-S and Clara-H in the Old West. But we know that the Doc and Clara we see at the end of BttF3 went farther into the future to hover-convert the train. Since Doc-S and Clara-H can’t return to Timeline-H from the future, the family that arrives in Timeline-H, and subsequently creates Timeline-I, must have come from another timeline. And since Doc, being from the future, cannot have come from the same timeline as Clara (Law #2) he must have come from Timeline-Q and she from Timeline-P.

Trust me, it makes sense.

In the end, Doc-Q and Clara-P fly off to-

XXXX, TImeline-?

…some other timeline, to perpetuate the paradoxes and infinite timelines by further meddling in the space-time continuum.

That’s it! It’s all pretty straight forward, right?

Now the astute reader may ask, “If everything is happening in separate timelines, then why does Marty begin to fade away when George-B and Lorraine-B don’t kiss at the Enchantment Under the Sea Dance?”

That’s a great question!

And you thought it was over!

As I stated numerous times, the events between different timelines have a tendency to play out similarly. The same set of events always sent Marty into the past to begin messing things up in 1955. So while it may look like Marty-A is witnessing his parents fail at romancing, thus causing him to never exist, we have to remember that he is witnessing the failure of Lorraine-B and George-B, who go on to give birth to Marty-B. So then why is Marty-A disappearing?

Because some other version of Marty, Marty-O we’ll say, is meddling with the events in Marty-A’s past, causing a ripple effect through the multi-verse that causes Marty-A to almost never be born. But just as Lorraine-B and George-B get together, so do Lorraine-A and George-A.

“But if Marty-A is the original, and he is the first to travel back in time, then how could anyone have altered his past? 1955-A should be free of time-travelers!”

What we must remember is that Marty-A is the origin point for our perspective of the story. However with multiple timelines, it’s most likely not the one timeline where time travel was first breached. The alphabetical denominations for the various timelines is just so that we can make sense of them. But they actually all exist side-by-side and simultaneously.

But actually it’s more

So the time travelers aren’t just falling deeper down through a stack of timelines initiated by Marty-A, but rather bouncing back and forth through an infinite number of timelines created by the infinite number of minute changes created each time another time traveler goes back in time.

What’ll really bake your noodle is when you realize that every time I mentioned a time traveler from 'an unseen timeline’, that their earlier arrival had also caused a new timeline upon their arrival. Meaning that when Marty-A arrives in a timeline where another time traveler already exists (i.e. Marty-Y or Old Biff-V) that he’s splintering a previously splintered timeline. And if each of those timelines had some version of Doc in the Old West, then it was a splinter of that splinter that Marty-A just splintered AGAIN!. It’s entirely too much to comprehend…

While you ponder that one…

Summing it all up, the Back to the Future trilogy shows us:

7 Timelines on Screen:

Timeline-A: Lower-Middle Class McFly World

Timeline-B: Upper-Middle Class McFly World

Timeline-C: Future Hill Valley

Timeline-E: Hell Valley

Timeline-F: Where Doc-Z and Marty-A return to 1955

Timeline-H: The Old West

Timeline-I: Created when Doc-Q and Clara-P arrive via flying train.

But we can deduce:

21 Total Timelines:

Timeline-A: Lower-Middle Class McFly World

Timeline-B: Upper-Middle Class McFly World

Timeline-C: Future Hill Valley

Timeline-D: Created by Old Biff and continues to exist when he returns to 2015

Timeline-E: Hell Valley

Timeline-F: Where Doc-Z and Marty-A return to 1955

Timeline-G: The destination of Doc-Z when lightning strikes the DeLorean

Timeline-H: The Old West

Timeline-I: Created when Doc-Q and Clara-P arrive via flying train.

Timeline-O: The origin of the Marty who meddles with the events of 1955-A

Timeline-P: The origin of the Clara we see on the Hover-Train

Timeline-Q: The origin of the Doc we see on the Hover-Train

Timeline-R: The origin of the Jennifer found on the porch swing at the end of BttF3

Timeline-S: The origin of the Doc that Marty-A meets in the Old West

Timeline-T: The origin of the Doc that dies in the Old West

Timeline-U: The origin of the Marty that Marty-A is trying to avoid in 1955-F

Timeline-V: The origin of the Old Biff that we see giving the Almanac to Biff-F

Timeline-W: The origin of the Old Biff we see returning to 2015

Timeline-X: The origin of Middle-Aged Jennifer

Timeline-Y: The origin of Middle-Aged Marty

Timeline-Z: The origin of the Doc who appears at the end of BttF1