Some ideas are:
- You branch off into another timeline and your actions make no difference to the previous timeline
- You’ve already taken said actions but just didn’t know about it so nothing changes
- Actions taken can have an effect (so you could suddenly erase yourself if you killed your parents)
- Only “nexus” or fixed events really matter, the timeline will sort itself out for minor changes
- something else entirely
The past, present, and future do not exist as separate states.
Imagine a vast array of all possible states of matter in the universe. Imagine reality has a finite spacial resolution. With a series of numbers, or even a single very large number, you could provide a unique identifier for every possible arrangement of matter in the universe. The positions of every star and galaxy. The detailed interactions of every quark. Imagine a list or array that would have a number of entries equal to some indecent multiple of “ten to the ten to the ten…” Imagine all these possible states, every possible configuration the matter of the universe could occupy.
Then realize…All of these possible states exist at once. They are all as real as any other. There is no preferred state. They all exist in some vast “10 to the ten to the ten” dimensional spacetime. What we perceive as the flow of time is simply us moving from one of these states to another. But our consciousness cannot move arbitrarily between states. There are elaborate rules on which states you will be able to observe dependent upon the states you previously observed. We call these rules the laws of physics.
So when you travel through time, you are simply altering your path on this vast multiverse of possible realities. There is no “real” reality. They are all real. Every possible configuration of the matter and energies of the universe physically exist concurrently.
There are no timelines to split or erase, because there are no timelines. There are just conscious minds moving through a near-infinite array of possible “nows.” And all of the nows exist simultaneously. There is no real one. From the perspective of a “time traveler,” it will seem like they changed “the future.” But the truth is the very idea of a past, present, and future as distinct entities is madness. We’re just consciousness drifting through the continuum, from one of the near-infinite nows to another.
That’s a really long way to say “the first one”.
I think it’s the 2nd option
It’s just the first one, only specifically a version where all timelines exist and you simply navigate them. I can see how it might feel like the second one because the timelines already exist, but from one’s subjective viewpoint it’s #1.
I think the first one leaves open what you do, as alternate actions lead to an alternate timeline. The second is more “read-only”, similar to what OP laid out.
The only difference between the first option and the response is that the response posits that all possible timelines exist in advance and rather than generating a new timeline with your decisions, you simply navigate to the one that represents them. It’s a distinction without meaning, especially because the first option doesn’t strictly specify whether the timelines existed in advance or not. It simply says “you branch off into another timeline” with no requirement that it be one generated as a result of your actions.
The second option is called “closed loop” or Novikov self-consistency and specifically requires that the outcomes of your choices align with the past already as defined, simply in ways you did not know. It’s what they use in 12 Monkeys and the 3rd Harry Potter book, and it limits free choice, unlike the first option and what the above poster’s response stated.
I think what you’re doing is combining closed-loop and multiverse theories to say that the multiverse theory IS closed-loop simply because the multiverses existed in advance, whereas closed-loop is intrinsically single universe/timeline.