Time travel has always been one of the more complex storytelling devices and often has to outline a set of rules for the storyline to make any sense. One of the biggest problems in telling a time travel story is not just the rules that the story puts forward, but the audiences preconceived notions about time travel. And a big part of how audiences think of time travel is thanks to Back to the Future.

The 1985 hit is a pop-culture classic that no only redefined what sci-fi movies could be, but also remains one of the best examples of time travel storytelling that we’ve seen to date (even if it doesn’t quite line up with a modern-day understanding of time travel). But before we get into the various timelines that are created throughout the movies, it’s worth looking at the rules of time travel the Back to the Future movies establish and follow.

Over the years many fan theories have outlined several apparent plot holes and paradoxes, but a good number of them can be explained away by actually looking at Doc Brown’s own explanation of time travel (rather than how we imagine it works or comparing it to other examples).

Whilst detailing how the various timelines work to Marty in Back to the Future II, Doc. explains that each time someone jumps backwards in time they create a wholly new timeline, and thus destroy the version of events they left behind, this new timeline creation applies no matter how big or small the changes the time traveller makes are. And so every time we see a character use a time machine to go back into the past they are creating a wholly new timeline, this, however, doesn’t apply to jumps forward in time, and so Einstein’s jump one minute into the future in the first movie doesn’t create a new timeline.

Timeline 1

The original set of events, that we’ll refer to as ‘Timeline 1’, is pretty much everything that happened leading up to Marty’s first trip back in time in 1985. Based on what we eventually find out across all three movies, we know that Hill Valley was founded in 1850, with the McFly family moving from Ireland to America during the early 1880s. The famous Hill Valley courthouse clock arrived in Hill Valley on September 5th 1885, around the time of infamous outlaw Buford ‘Mad Dog’ Tannen.

Hill Valley eventually grows into is your typical American town, and in 1955 a great storm hits, striking and pausing the town’s clock. On the same night, George McFly and Lorraine Baines go to the Enchantment Under the Sea dance together, this happens a few days after Lorraine’s father hit George with his car, after which Lorraine became infatuated with him. The two fall in love and by 1985 have three children; Dave, Linda, and Marty.

George’s high school bully, Biff Tannen, continues to take advantage of George, and by 1985 is his supervisor. George and Lorraine’s youngest child, the seventeen-year-old Marty, is at high school, dating Jennifer Parker, and works for/with Doc. Brown, an eccentric and reclusive scientist.

As an audience we get the general sense that neither George nor Lorraine are overtly happy; Lorraine is implied to have a drinking problem and George is unfocussed and is still being bullied by Biff, on top of that their house is run down, and their three kids are portrayed as relatively unmotivated or unsuccessful.

As Doc calls Marty to meet him at Twin Pines Mall at 01:00 AM on October 26th 1985, Doc reveals the DeLorean Time machine. Shortly after the reveal Libyan terrorists (that Doc stole the plutonium, to power the time vehicle from) arrive, shoot Doc and chase Marty, he quickly jumps into the DeLorean and accidentally sends himself back to 1955 – thus creating ‘Timeline 2’.

Timeline 2

With Timeline 2 being the focal point of the first movie all of the setup, pre-1955, is exactly the same. After escaping 1985 Marty arrives in 1955 where the Twin Pines Mall he left behind is yet to be built and is instead still the Peabody farm (that Doc previously mentioned). Whilst driving away from the farm (and destroying one of the two pine trees at the farm’s entrance) Marty confusedly makes his way into the centre of Hill Valley. Once there he slowly begins to realise he really is in 1955 and comes across the seventeen-year-old version of his father.

After seeing his father bullied by Biff (and deciding George is a total loser), Marty follows George and discovers he’s a ‘peeping tom’ who spies on Lorraine getting undressed. As George falls from the tree, wherein the first timeline he would have been hit by Lorraine’s father’s car, Marty instinctively jumps to George’s rescue, pushing him out of the way and gets hit by the car himself.

Marty wakes with his mother at his bedside and assumes it was all a dream and that he is back in 1985. Unfortunately for him when the lights go on he sees his mother is a lot younger than she should be and realises he is still in 1955. To make matters worse she is now infatuated with Marty rather than George, as happened in Timeline 1.

Marty then goes to the 1955 version of Doc Brown for help in repairing the time machine (so that he can get “back to the future”). But whilst they do so, Marty assumes the identity of Doc’s nephew ‘Calvin Klein’ to ensure his parents get together (and that he and his siblings are born).

Doc and Marty fix the time machine and, utilising the lightning bolt that Marty knows will hit the clock on the night of the dance, he arrives back in 1985. He quickly heads to the Mall to save Doc from the Libyans (after 1955 Doc refuses to take a letter from Marty explaining his eventual death). 

But when Marty reaches Doc, after seeing his past self escape in the DeLorean and head for 1955 (closing that time loop), he realises that Doc did read his letter in the past, and was wearing a bulletproof vest.

Soon enough Marty discovers that the Timeline 2 version of his family is significantly more successful, happier, and richer. As the first movie draws to a close, and everything seems to have wrapped up nicely in Timeline 2 Doc reappears from the future, telling Marty and Jennifer they have to go back to the future with him, and thus with his jump back from the future, he creates ‘Timeline 3’.

In short, the main differences between Timelines 1 and 2 revolve around Marty saving George from getting hit by the car and thus setting off a chain of events that (if they continued) would prevent him and his siblings from being born. But even after he ‘fixes’ everything Marty’s presence in the past continues to change a huge amount of things from Timeline 1, namely getting George to stand up to Biff. 

This, in turn, ensured a much more confident version of his father, who went on to become a successful sci-fi writer. Marty running over one of the pine trees at Peabody’s farm also means that in Timeline 2 the mall is called ‘Lone Pines’ Mall rather than Twin Pines, and with George taking the name ‘Darth Vader’ and other elements from Star Wars and Stark Trek from Marty’s pretend alien encounter, neither franchise would exist (at least not in their Timeline 1 forms).

With George much more confident the McFly family is a much happier version of its Timeline 1 counterpart, and his siblings appear to have better jobs, Biff now washes the McFly family cars instead of being George’s supervisor, and Marty finally has the car he always wanted.

Timeline 3

Pretty much as soon as Back to the Future II starts we learn how Timeline 2 plays out for Marty and Jennifer, and it isn’t exactly the happy ending we thought. 

The day after Marty got back to 1985 he was coaxed (by being called a ‘chicken’) into a street race that not only damaged his hands, affecting his ability to play the guitar but ended up in a lawsuit, setting Marty up for a future of financial problems.

Consequently, he and Jennifer get married in the ‘Chapel o’ Love’, go on to live a somewhat unsuccessful life much like George and Lorraine in Timeline 1, and eventually, both of their children end up in jail, thanks to Biff’s grandson ‘Griff’.

Learning of all of this Doc decides to travel back to 1985 (thus starting Timeline 3), intending to get Marty and Jennifer to go to 2015 with him and help stop their children from getting into trouble.

As Doc and Marty play out Doc’s plan (and take on the cyborg Griff) Marty gets the idea to buy the ‘Gray’s Sports Almanac’, which chronicles all of the sporting results from 1950 to 2000.

Marty’s idea is to take the book back with him to 1985 and place a series of bets that he already knows the result of. But Doc stops him from keeping the almanac, and instead, the two retrieve Jennifer and head back for 1985, assuming everything has been fixed.

Unbeknownst to Doc and Marty however Grandpa Biff from 2015 overheard their conversation about the Sports Almanac and decided to steal the DeLorean and give the almanac to his 1955 self (copying Marty’s plan). And so when Doc, Marty and Jennifer arrive back in 1985 they quickly realise it’s a very different world from the one they left and work out that Grandpa Biff created Timeline 4.

One timeline problem here is how Biff manages to go from giving his past self the Almanac, and creating Timeline 4 with that time jump, back to the Timeline 3 version of 2015 to return the DeLorean.

Timeline 4

The fourth timeline we see created is the first to be a drastically different version of events from what we already know. Although we don’t technically see much of it we learn that Grandpa Biff (from 2015) went back to 1955 and gave his teenage self the Sports Almanac, which in turn led to Biff making a number of successful bets, his business empire BiffCo, and with that the resultant control over and decline of Hill Valley, murder of George McFly, and marriage to Lorraine.

This timeline exists as a direct result of Grandpa Biff’s travelling from 2015 to 1955, but when Marty, Doc, Jennifer, and Einstein leave 2015 for 1985 their time jump, based on Doc’s rules of each jump backwards creating a new one, creates Timeline 5.

Timeline 5

With Timeline 4 revolving around Grandpa Biff giving his former self the almanac, Timeline 5 follows suit, except this version, has Jennifer, Einstein, Doc, and Marty (coming directly from Timeline 3’s 2015). 

Pretty much as soon as he arrives Marty realises something is wrong with this Hill Valley, and he quickly discovers that Hill Valley has descended into a lawless, almost dystopian version of its former self, thanks to Biff’s influence.

With Jennifer knocked out, Doc and Marty discover that once Grandpa Biff from 2015 (in Timeline 3) went back in time and gave his past 1955 self the Sports Almanac, the 1955 version of Biff went on to become a millionaire. He then turned his money into a business empire and now owns a giant hotel in the middle of Hill Valley as well as most of the town, and police force. We also find out that in this reality Doc. Brown has been committed to a mental asylum, that Biff went as far as murdering George McFly to finally marry Lorraine, and that Marty has been sent out of the country to a boarding school.

Doc works out (thanks to Grandpa Biff’s cane breaking in the DeLorean) what has happened, and decides they need to find out when this version Biff first got the almanac from the Timeline 3 2015 version of himself self, and then stop him using it. Marty quizzes Biff on when he received the almanac, who in turn reveals that when his ‘distant relative’ gave it to him in 1955 he also warned him of a ‘kid’ and ‘crazy scientist’ who might one day come asking about the almanac, and that if they did, Biff should kill them.

As Marty runs from Biff and his goons (now armed with the knowledge of when Biff got the almanac) he and Doc escape and head back to 1955, and with that jump into the past create Timeline 6.

The main differences of Timelines 4 and 5 again stem from the day of The Enchantment Under the Sea Dance in 1955 (to the point where Doc even questions if this is a mere coincidence or if there is a possibility that there is something special about that day). The majority of events Marty set in motion in Timeline 2 still happen up until the early ’70s, not counting Biff’s rise to power. In 1973 however, Biff murders George McFly (who was on his way to collect a writing award), in the same year Biff marries Lorraine (who already has her three children with George) and sends Marty off to an overseas boarding school.

Timeline 6

The sixth timeline plays out as the earlier part of Timeline 5 (where Grandpa Biff gives his younger self the almanac), except this time Marty and Doc are working behind the scenes to steal it back and stop 1955 Biff from ever using it.

After yet another chase involving Biff, Marty, hoverboards, and manure Marty and Doc eventually succeed in getting the Sports Almanac from Biff, but just before they are able to (finally) head back to their 1985 (or at least the altered Timeline 2 version of it) the DeLorean is struck by lightning, and Doc along with the time vehicle disappear completely.

As Marty stands in the rain, yet again stranded in 1955, a car approaches and a man claiming to be from Western Union delivers a letter that has been held for seventy years with strict instructions to send it to that exact spot at that exact time.

The letter reveals that Doc has been sent (via the lighting strike and a time machine malfunction) to the year 1885, and as a result has created Timeline 7. Interestingly Timeline 6 is the first timeline to feature two versions of Doc, Marty, and Biff at the same time.

Timeline 7

Timeline 7 features the earliest changes to a timeline so far and see’s Doc living in the Old West. Doc’s letter to Marty explains that he has been living in the year 1885, and works as a blacksmith in a very early Hill Valley.

He goes on to explain that he can’t get back due to damage to the DeLorean and that suitable replacement parts won’t be built until 1947, he adds he is quite content with his new life in his favourite time period.

He also mentions that he has hidden the DeLorean in a cave at the Delgado mine for Marty so that with the help of the 1955 Doc he can repair it and get himself back to 1985.

Finally, Doc asks Marty not to come back for him and that once he returns to 1985 he should destroy the time machine as it’s far too dangerous (having already caused a huge number of problems). Although not exactly happy about it Marty agrees, but whilst he and 1955 Doc retrieve the DeLorean Copernicus (Doc’s dog in 1955) leads them to a grave just outside the cave.

The headstone reads; “Here lies Emmet Brown, died September 5th 1885, shot in the back by Buford Tannen over a matter of eighty dollars.” With September 5th being only a week after Doc writes the letter for Marty, he decides to go backwards in time to 1885 to save Doc from Buford ‘Mad Dog’ Tannen, and in doing so he creates Timeline 8.

Given that Timeline 7 leads into some version of the events as we understand them (with 1955 Doc having just sent the original Marty back to 1985 when this latest Marty comes to find him), the only real differences here are Doc’s presence and murder by Mad Dog Tannen, and of course the survival of Clara Clayton. Doc’s tombstone ends with “erected in eternal memory by his beloved Clara”. And so as Marty witnesses in Timeline 8 Doc must have saved Clara from falling down Shonash Ravine, as she had done before Doc went back to 1985.

Timeline 8

After seeing the details of Doc’s murder on his tombstone, and the subsequent confirmation of both Doc’s presence in 1885 and Mad Dog Tannen’s reputation at the Hill Valley library. Marty and 1955 Doc decide Marty must travel back to the Old West and warn Doc of his fate.

After escaping a battle between Native Americans and Federal forces, cutting the fuel line on the DeLorean, and meeting his great grandfather Seamus McFly (whose wife looks suspiciously like Lorraine McFly – meaning the McFly men clearly have a certain type) Marty arrives in Hill Valley, and quickly goes up against Buford Mad Dog Tannen. Unlike his encounters with Biff and Griff, Marty isn’t able to outsmart Buford, who proves a little more dangerous and is only stopped from killing Marty by Doc’s arrival.

After he saves Marty, Doc quickly learns of his fate but also tells Marty that the broken fuel line isn’t as simple a fix as Marty would have thought (given that refined fuel won’t be easily accessible for years).

After horses can only get the DeLorean up to around 30 miles per hour, the two decide that the only option is highjacking a train that could push the DeLorean up to the required 88mph.

Not long after this realisation, Doc ends up rescuing Clara Clayton from falling into Shonash Ravine, and almost immediately falls in love. Whilst Doc prepares the time machine he also wooes Clara, Marty ends up arranging a shootout at dawn with Buford Tannen and the picture of Doc’s gravestone switches to say ‘Clint Eastwood’ (Marty’s 1885 alias).

Eventually, after copying the actual Clint Eastwood from A Fistful of Dollars (the movie we saw alternate 1985 Biff watching in the hot tub) Marty escapes his shootout with Buford and gets Doc to the train. The two take over the train and begin to push the DeLorean as the engine gains speed.

Before Doc can get into the DeLorean with Marty however Clara arrives, and as she falls from the train is quickly saved by Doc, the DeLorean hits 1885 and sends Marty back to the future. Almost as soon as he arrives Marty is forced to jump from the DeLorean as a train smashes into it, finally destroying the time machine.

After Marty reunites with Jennifer and avoids the ill-fated drag race with Needles, Doc and Clara reappear in a flying, time travelling, steam train, accompanied by their two children Jules and Verne (creating Timeline 9, or possibly more as it’s clear they are hopping around all over).

Timeline 9

Doc explains to Marty that everything has been fixed, nothing is set in stone and that now both Marty and Jennifer’s future is whatever they make of it.

As implied by the ‘Erected in eternal memory by his beloved Clara’ on Doc’s Timeline 7 tombstone, we see Doc save Clara from falling into Shonash Ravine. Instead, we see that when Marty returns to 1985 the ravine is now known as ‘Eastwood Ravine’, a tribute to his heroics and sudden disappearance under the alias of Clint Eastwood in 1885.

We also see the drag race the Timeline 2 2015 version of Marty was coaxed into by being called a chicken, here, however (having learned a few lessons throughout his time travelling and Jennifer’s intervention) Marty doesn’t race, and therefore doesn’t crash into the Rolls Royce, which in Timeline 2 damaged his hands and went on to ruin Marty and Jennifer’s lives.

The biggest thematic and character change going into Timeline 9 is Marty actually learning something, Marty is the perfect hero throughout the series but even in the first movie he rarely learns from his mistakes (or even the mistakes of his parents), and is instead still hung up on more material things like getting the car he always wanted, but by the end of the third movie we see he cares less about people calling him ‘chicken’ and is growing into his own person. The end of the third movie sets Marty up to take Doc’s advice and make his own future.

Timeline 10

The tenth timeline didn’t arrive until almost twenty-five years after the third Back to the Future movie, and features in a special in the 30th-anniversary box set of the trilogy.

The short details Doc Brown’s efforts to fix the future (specifically the version of 2015 we saw in the second movie) and avert a Nuclear Holocaust in the year 2045. Via Doc’s message to Marty, we learn that Griff Tannen accidentally caused this Holocaust by uploading a virus that set off every Mr Fusion in the world, eventually, Doc fixes Griff’s mistake (making sure he goes back to jail). But as Doc celebrates his victory, he realises he still has the ‘Quantum Mind Jar’ that he meant to dispose of in 2075, after this discovery another Doc Brown appears (perhaps creating the 11th Timeline?), and as the two are confused at each other’s presences, the short ends.

Back to the Future is one of the most iconic movie franchise of all time, and even though there are a few plot holes here and there, overall the ten (or more) timelines are very well written, immensely complex and brilliantly thought out.