In one of its earliest scenes, Back to the Future’s ending, everything seems to be fixed by Marty.

However, Doc and Marty don’t have an easy time getting to this point. The duo face constant problems, both from George’s general cowardliness to Lorraine’s inconvenient crush on her own future son, Marty. The first of these problems occurs when Marty arrives in 1955 and seeks out the younger version of his father, George McFly. Marty’s arrival triggers a clever subversion of what is known as the Grandfather Paradox. A time travel problem helpfully explained by Space.com, the Grandfather Paradox refers to a logical problem wherein a time traveler kills their grandfather in the past, preventing their own birth.

Marty McFly Flipped The Grandfather Paradox By Saving George From Being Hit By A Car

Marty Saving George From A Car Accident Flipped A Famous Time Travel Paradox

Instead of killing his grandfather before he is conceived, Marty saves his father’s life before Marty himself is conceived in Back to the Future. In an interesting riff on this premise, Marty is arguably also the one to blame for his father’s near-death experience, since George runs away from him and toward oncoming traffic because he is freaked out by Marty. Back to the Future’s many clever details pay off throughout the trilogy’s knotty, complex time-twisting story, but this scene provides one of the franchise’s earliest instances of flipping sci-fi conventions on their head to offer viewers something fresh.

Marty was almost never conceived due to his intervention in George’s early life.

Marty saves George from being hit by a car after George runs away from him and into the car’s path. Ironically, the effect was the same as the Grandfather Paradox, as Marty was almost never conceived due to his intervention in George’s early life. Back to the Future cleverly actualizes this threat through a photo of Marty that fades away whenever he has altered the timeline enough to prevent his own conception. Back to the Future’s George McFly needs a lot of coaching from Marty before he can save his own future, meaning Marty repeatedly risks accidental self-annihilation.

Marty Saving George Had The Same Effect As The Grandfather Paradox Would Have

Marty’s Fortunes Didn’t Improve Despite Him Saving George

Marty saving George from being hit by a car is not enough to ensure his own conception later on, but it is the beginning of Marty turning around his father’s fortunes. In Back to the Future’s ending, Marty has set things right in 1955 and his mother and father are now happier, more stable, and free from the machinations of their high school bully Biff. Back to the Future Part II then sees Marty and Doc travel to the future and then back to 1955 again to solve some new problems, ensuring the Back to the Future movies never become too repetitive.

Source: Space.com