When Marty McFly first goes back in time in a DeLorean souped up into a time machine in the film Back to the Future, he triggers consequences which could blink him out of existence or improve his future life. Subsequent travels by him and others also cause minor and major effects on his family and surroundings. Examples include the triviality of the change in name of a mall in 1985 from Twin Pines to Lone Pine due to Marty driving over a young pine tree 30 years before, or the personality reverse of his father from mealy-mouthed white collar worker to ass-grabbing sci-fi novelist.
These changes are all exhaustedly detailed in a timeline of the events leading up to and happening in and around scenes of the film trilogy. As each use of the time machine alters time itself, not one but eight timelines are needed to visualise what happens. The most complete timeline can be found on the fansite Futurepedia, while a decent information graphic has been made by another fan of the films.
The first attempt to describe intertwined time travel changes in the film most likely showed up on Usenet postings about the film in the early 1990's, and expanded into a wiki entry in the mid 1990's. In 2004, a version of the timeline was added to Wikipedia, and subsequently edited for the next 5 years.
The timeline is still on Wikipedia --if you are in the right time and place-- for it was deemed that the timeline be moved into the main page for the film. Soon after, editors then considered the information to be 'original research' and thus not within Wikipedia's scope of being an encyclopedia of knowledge and events, rather than a repository of essay, compositions or obsessive trivium. The timeline in the film page was removed, yet because Wikipedia keeps a record of all edits, you can still find the timeline.
I write this on the tenth anniversary of Wikipedia's creation, and this is my tribute to a knowledge resource that is beyond anything I could have imagined in 1985, or even 1989, when I saw Back to the Future II, which showed a future in 2015 of flying cars, hovering skateboards and self-lacing sneakers. Here is a place I can use as a springboard for discovering anything I want to begin learning about history, science, art, places and philosophy. It presents what it assumes is a neutral point of view and as such tries to show the truth as what is known at the time... and can be updated as more facts become known. At the same time, there is full disclosure: when someone tries to insert a fiction into a fact, there is a history of each page available, allowing one to see what's been changed. Compared with the agendas of encyclopedias of the 20th century and the rewriting of history so prevalent in school textbooks, this online experiment proves the grassroots world sharing hopes of early Internet promise. With a homogenised language and the freedom of anybody being able to edit it, Wikipedia can be easily dismissed-- by the same people who use it as the first point of call for fact-checking and research. The curse of its limits is its blessing: it has become exactly what it set out to be.
At the end of Back to the Future, Doc Brown collects Marty and his girlfriend in his car and heads off to the future as his car takes flight, saying 'Where we're going, we don't need roads.' Four years later, in the sequel, the same scene is repeated at the beginning of the film, except the actress playing the girlfriend has changed. I always thought it was changed because the filmmakers thought the original actress wasn't up to scratch, but, Wikipedia tells me (with a reference to an article by someone who interviewed her) she had to drop out due to her mother's illness. It seems like a trivial thing, but this knowledge makes my appreciation of the films just a bit more human. Thanks Wikipedia!