Wouldn't time paradoxes render the plot of "Back to the Future" impossible?

Don’t ruin my childhood. DON’T DO IT.

The short answer is that yes, that’s one view of the way the universe works. There is only one timeline, and messing it up means you’ve written yourself out of the universe. (This is the view Back to the Future takes, because it’s much more fun to have The Laws of Physics be an antagonist alongside Biff.)

However, you’re right. It results in a paradox. Instead, let’s assume that the universe isn’t so fixed as to have the One True Timeline. In this case, Marty’s component atoms won’t spontaneously disappear no matter what happens. Think of Marty traveling through time like he’s on a canoe in a river. Marty will float down the river at a set pace for his entire life, or he can paddle back up the river and take a different fork.

Imagine Marty comes to fork ABC in the river, takes path A for a bit, and then litters on the shore. Now, if he paddles back up the river and takes path B or C instead, the litter won’t disappear: he’s already littered. He’s double dipping on the river, not replacing his actions.

If you think of time as a dimension just like length, width, and depth, Marty can travel back up the time stream (in this case, it’s especially odd, because he’s traveling to before he’s even born) freely. But his component atoms have no memory: they don’t “know” that he’s accidentally prevented his parents from marrying. The only thing he can change is what kind of world he returns to in 1985: Marty’s component atoms don’t care whether he’s on path A of a river, path B of a river, the original 1985, the improved 1985, or even 1955. They’ve already been assembled once, and traveling to 1955 is no different to them than traveling to 1986, no matter what happens in 1955.

This is why you shouldn’t attempt to learn advanced physics from a movie.

No. Everything in BTTF is correct because it’s is a great enough movie that it changes the rules of time an space. If there was no gravity or the Sun revolved around the Earth the movie would still be correct.

totally…yes!!!

sorry but don’t dis the Back to The Future!!! Love that film.. I’m with @lefteh Don’t ruin my childhood film by trying to make sense of it PURLEESE!

You mean to tell be Back To The Future wasn’t accurate with its temperal physics? Whoa!

Iirc in Part 2 the Doc explained that they were indeed operating in an alternate Reality System.

This is where the phrase “it’s just a movie” comes from.

Not in a multiverse containing parallel universes.

Fact from fiction, trth from diction. One cannot time travel the universe, in my opinion, is much like the body, everything is interconnected. I could not send my brain back to the time of Caesar, my lungs back to the American Revolution, and my heart to the Battle of the Bulge while leaving my body here. The brain would die because there would be no blood or oxygen to keep it alive, and so on. My brainless, lungless, heartless body would surely die for all the organs would die for lack of oxygen because no lings or heart to handle that. Likewise you could not send the moon, or Saturn back in time while leaving the rest of the solar system here, either it all goes back or none of it could. It would take way more than 100 sextillion watts of power for instance to send the whole universe even the parts unknown back in time. If you sent the moon back in time for instance, would not someone miss it in the sky? Where would this time reversal stop? Just at this solar system or maybe the next 5 solar systems? It all has to go back or none of it could