The Past Future, Future Past, and The Veracity of Time Traveling

Before we begin, let me just tell you all right now that this one's a head-hurter, so tune out now if you don't want, well, your head to hurt. So, here we go. In this blog entry, as promised, I will be comparing time travel theories as presented in the fabulous "Back to the Future" trilogy and what I believe is the best film franchise of all time, the "Terminator" series. Unfortunately, I'm not going to have enough time or energy to consider "The Sarah Connor Chronicles" in this particular entry, but be on the lookout for an entry in the not-too-distant future pondering the theories that show has put out on the table.
Let's start with the Back to the Future trilogy. There's a scene in Part II that many people may overlook but is actually quite crucial to the whole mythos that Bob Zemeckis sought to create from the get-go. It's a scene that occurs about fifteen or twenty minutes before the credits roll. Marty has burned the book (Gray's Sports Almanac) that caused Biff's richness in the alternate 1985 seen halfway through the film. Doc's getting ready to set the time machine for re-entry into the 1985 he and Marty remembered before the time machine was created. Earlier in the 1985A timeline, right before old Biff attempted to kill Marty in his hotel, Marty took a book of matches from Biff's office desk that promote the luxurious hotel he has built with his riches. So back to the scene where Marty has just burned the book. Right after he does so, the aforementioned match book immediately transforms into an Auto Detailing matchbook--- our indication that the 1985A timeline has effectively been deleted from history and the natural timeline has been restored. Marty and Doc will experience said timeline when they return back to 1985 (which won't happen until the end of Part III). The timeline has been altered without directly affecting their current selves, as Doc had said would happen earlier in the movie.
The Back to the Future trilogy works on events that HAVE happened already, and Doc's constant concern is that with his time traveling experiments, he may be interrupting the space-time continuum. For instance, Marty's purchasing of the Sports Almanac in 2015 was what resulted in the creation of the Alternate '85, where Biff was drunk with power, his mother was forced to marry Biff, and Biff had killed Marty's father. Had Marty not've burned the almanac, the space-time continuum would've been interrupted. But due to the book being burned in 1955, that ensures that Biff won't make the millions of dollars he made in the alternate timeline between 1958 and 1985. Traveling back to the future (1985) would no longer yield a horrible world where Biff Tannen practically ruled it. But Doc is struck by lightning and Marty feels obligated to go back in time to 1885 to save his time-traveling pal. In order to do so, he needs to uncover the time machine in a place where Doc has buried it after he arrived in 1885. He turns to the other Doc Brown, the 1955 one who sends Marty back to the future in Part I. DIRECTLY following sending the other Marty back to 1985, Marty 2 comes up to him telling him he's back from the future and needs to be sent back to the PAST. If your head's hurting right now, don't worry, mine is too.
In 1885, Doc falls in love, Marty nearly gets killed after making enemies with Biff's ancestor and it's up to Marty to convince Doc to come back with him to 1985 once they can find a way to get back to 1985! But nevertheless, Marty does end up getting back to 1985, even though Doc decides to live a time-traveling life with Clara by the movie's end. For all intense and purposes, the natural timeline is restored by the end of Part III. In 1955, George and Lorraine fall in love, with the help of one Calvin Klein (aka Part I Marty), Marty gets back to the future with the help of Doc, etc. In 1985, Biff is George's bitch due to Marty's intervening at the Enchantment dance (he convinces George to stand up for himself which Lorraine goes gaga over), Marty is a normal teen, his siblings are normal, and he's madly in love with girlfriend Jennifer. In this franchise, the time travel isn't essential to anyone's life per se, but rather it is essential to time itself (once a time machine is created, time itself is inevitably altered from the first "experiment". In this case, that first experiment is Doc sending Einie one minute into the future at the beginning of Part I). The case is different, however, for consideration number two: the Terminator films.

Stay tuned for Part II of this hopefully enlightening blog.