In this article by Vanity Fair, Michael Waldron talks about the rules for time travel set by Loki (2021):
Marvel already made its case for how time travel works in Avengers: Endgame, but that, Waldron points out, “is the way the Avengers understand it.” With a TV show it’s a little different. “I was always very acutely aware of the fact that there’s a week between each of our episodes and these fans are going to do exactly what I would do, which is pick this apart. We wanted to create a time-travel logic that was so airtight it could sustain over six hours. There’s some time-travel sci-fi concepts here that I’m eager for my Rick and Morty colleagues to see.”
This article was posted before Loki began airing. Now that Loki has finished airing and we've seen the full breadth of time travel involved in the story, what are the specific rules and logic that govern time travel in the TV series (and most likely also the larger Marvel Cinematic Universe)?
Avengers: Endgame had that excellent scene where they laid out the rules for time travel as the Avengers understood it and said it doesn't work like the Back to the Future:
Professor Hulk: I don’t know why everyone believes that, but that isn’t true. Think about it: If you travel to the past, that past becomes your future, and your former present becomes the past! Which can’t now be changed by your new future!
The only other scene I remember in Avengers: Endgame was the one where the Ancient One talks about not destroying timelines:
Ancient One: I'm sorry, I can't help you, Bruce. If I give up the Time Stone to help your reality, I'm dooming my own.
Bruce Banner: With all due respect, I'm not sure that science really supports that.
Ancient One: The Infinity Stones create what you experience as the flow of time. Remove one stone and that flow splits. Now, this may benefit your reality but my new one, not so much. In this new branched reality, without our chief weapon against the forces of darkness, our world will be over run. Millions will suffer. So, tell me Doctor, can your science prevent all that?
Bruce Banner: No, but we can erase it. Because once we are done with the stones, we can return each one to it's own time line at the moment it was taken. So, chronologically, in that reality, they never left.
In Loki, our understanding of time travel was stretched across the whole TV series and we didn't get an easy two scene explanation of how time travel worked. The episode where Loki gets oriented has a video that explains time travel and timelines as the Time Variance Authority understands it, but we learn more about timelines and how time travel works as the series progresses.
How are the rules of time travel in Loki similar to those in Endgame, and how do they differ? What new rules are created in Loki? What are the specific time-travel logic rules that Michael Waldron talks about in the article with Vanity Fair? What do the rules for timelines and time travel look like for the future Marvel Cinematic Universe films?