Back to the Future sets up a couple of different problems from the beginning of the film that have repercussions on the decisions Marty makes throughout its course. Several of those decisions hinge entirely on Doc Brown and what he imparts to Marty about time travel. When Marty is in 1955, he is working with the ᴀssumption that Brown Doc has just been killed, as well as with the knowledge that Doc thinks that messing with the original Back to the Future timeline could have catastrophic consequences.
Over the course of the trilogy, more details about the rules of Back to the Future‘s time travel are revealed. Some of these details are explained by Doc’s theorizing, while others are shown through the consequences of Marty and Doc’s actions. Over time, Doc becomes more lenient about his policy of making decisions that could alter the timeline, and it’s likely that one key iconic Back to the Future scene during Marty’s time in 1955 led him to restructure his theories about time travel entirely.
Doc Firmly Believed That Messing With The Past Would Ruin The Timeline Forever
Doc Was Worried About The Consequences Of Messing With The Space-Time Continuum
Throughout Back to the Future, Doc Brown hammers in how dangerous messing with the timeline could be. This is a large part of the reason why Marty is so careful to hide his true idenтιтy; if his parents were to know that he was their son from the future, he could have disrupted the timeline even further with a changed variation of the grandfather paradox. Doc is right to be worried about that risk, as shown by the pH๏τo with Marty and his siblings fading from history.
What Doc doesn’t think about at first is whether messing with the timeline could also have positive consequences. From Doc’s point of view, there isn’t much reason to think about how they could improve the timeline, as his insistence on keeping it intact has led to him not knowing about many of the future’s details. Even if he thought about the idea of improving the future and realized that the timeline was malleable enough to be fixed without destroying it, it makes sense to be careful about just how much you purposefully change.
The Exact Moment Doc Realized The Timeline Could Still Be Fixed In Back To The Future
Doc Learns Of The Timeline Being Saved At The Same Time As He Learns About A Change To It
A post from user amanwhodrinks on Reddit gives insight into what Doc’s thought process might be when he realizes that the changes to the timeline aren’t as dangerous as he initially thought. Near the end of Back to the Future, Marty fills Doc in on both the repaired pH๏τo and his father hitting Biff around the same time, commenting that his dad had never done that before, broadcasting an obvious change to the timeline to Doc at the same moment that he shows that the timeline has been fixed enough to save the lives of himself and his siblings.
When Marty tells him about the punch and shows him the picture, Doc questions him, confirming the change to the timeline by asking, “Never?” to which Marty responds, “No, why?” Doc’s hesitation before responding with “Nothing” might appear to be a minor detail at first, but it could be a key moment for understanding Doc’s thought process during the rest of the film. It’s likely that this is a moment of realization for Doc that Marty might be going back to a slightly different 1985 than the one he originally came from.
The picture fixing itself has shown that the timeline has also been fixed enough to save Marty’s family, and this has happened even while the timeline is changing right in front of them.
The Reddit theory goes on to explain that this is the moment when Doc’s outlook on time travel changes. He had been going off the ᴀssumption that the space-time continuum was fragile and that they could destroy all of existence if they changed things too much. However, this moment is proof to Doc that the timeline isn’t as fragile as he initially believed. The picture fixing itself has shown that the timeline has also been fixed enough to save Marty’s family, and this has happened even while the timeline is changing right in front of them.
Doc’s Moment Of Realization Explains Why He Taped Marty’s Letter Back Together
George McFly Punching Biff Might Have Saved Doc’s Life
His moment of realization about the pH๏τo and the change to the timeline might have been what led Doc to tape up the letter and wear a bulletproof vest in Back to the Future toward the end of the movie. Confirmation that if he’s careful, the timeline could be changed without terrible consequences, might be the motivation Doc needs to check out what it is Marty wanted him to know.
He doesn’t get into this with Marty, instead just telling him, “I figured, what the hell,” but Doc is careful about the timeline throughout the course of the movie. It’s likely that this is a decision that took a lot more thought than he makes it seem.
Tearing up the letter originally was a decision made in the heat of the moment out of panic over the timeline, but Doc is smart enough to put further thought into the decision and hold onto the letter, even before he tapes it back up again. Every decision Doc makes about time travel in Back to the Future is thought out carefully, and despite his flippancy, this is likely no exception.
Source: Reddit
