I’m a physicist, and it took me a while to reconcile MCU time travel because Loki, Endgame and the Time Stone seem to contradict each other. Not because fictional time travel needs to obey real physics, but because they all get called “time travel” even though they are doing different things. In the process, I think I developed a fully consistent model of MCU multiverse time mechanics

The whole model (3 parts):

• Quantum Realm: changing the visited past creates another branching timeline.
• Time Stone: changing the past was already determined in the timeline. A timeline is the sequence of configurations of matter and energy in the universe, ordered by what the Time Stone itself experiences. No branch is created.
• TVA / Loki: acts on the whole tree of timelines from a higher-level TVA meta-time.

I’ve seen a lot of people reconcile pieces of this before, especially Endgame branching and the TVA. What I’ve done is take the explanations that can coexist, discard the ones that clash, and add a few pieces where the MCU leaves gaps. The result is one framework with three different operations on time.

---

   

1. Quantum Realm time travel: changing the past creates a branch

The grandfather paradox is the easiest way to show why branching is useful. If you travel back and kill your grandfather before you were born, the usual contradiction is obvious: if you were never born, who travelled back to kill him? In a branching framework there is no paradox. You came from the original timeline where your grandfather survived and you were born. Killing him creates a new branching timeline where he dies and the version of you native to that branching timeline is never born. The traveller is unaffected because the timeline they came from still exists, with an unkilled grandfather.

[See Image 1 Top: simple grandfather-paradox branching diagram]

Once that rule is in place, Endgame becomes much easier to read. Removing an Infinity Stone from the visited past immediately creates another branching timeline where the Stones have been removed. If you trace backwards along the Avengers’ original timeline, the Stones were never removed there at all. That is still the parent history (original timeline) they came from. Steve returns each Stone to the exact instant it was taken, so the Stone-less branch is prevented from forming, and the ancient one is happy.

The weirder consequence is 2014 Thanos. He leaves 2014, travels to 2023 and dies there. That should create a branching timeline where Thanos simply disappears in 2014. Steve still returns the Stones, so that timeline has all six Infinity Stones, but its Thanos is dead and the later Infinity War should never happen there. Before Loki, the TVA could prune that timeline if it fell outside the histories He Who Remains permitted. After Loki, branches are allowed to persist. Whether Marvel ever shows that exact no-Thanos timeline is another question, but it follows from the branching rule. But this is explained more in 3. below.

[See Image 2: existing Endgame branch / Stone-return timeline schematic]

> There is an obvious similarity here to the many-worlds interpretation of quantum mechanics: different realised outcomes from wavefunction collapse can exist on different branches instead of one outcome having to overwrite the others. That is the physical picture I am borrowing for the branching structure.

---

   

2. The Time Stone: changing the past was already determined to happen inside the timeline

The Time Stone is doing something different. Strange rewinding the apple does not need another timeline. The main definition I use from here onward is:

> A timeline is a sequence of configurations of matter and energy in the universe, ordered by what is observed / experienced by the Time Stone itself.

That is the reference parameter for the timeline whenever the Stone is involved.

memory of the reversed object BEFORE timestone reversal
A → B → C 

memory of the reversed object AFTER timestone reversal
A → B′ → C′ → D 

experience/memory of the TIMESTONE ITSELF (the only consistent definition of timeline)
A → B → C → rewind → B′ → C′ → D 

[See Image 1 Bottom: Time Stone-parameterized timeline]

That whole last sequence is what the timeline encodes, where each letter is the configuration of matter and energy in the universe. Strange deciding to use the Stone, the reversal itself, and whatever happens afterwards were all already part of what happens in that timeline. No branching occurs.

This is why ordinary Earth-time is not enough to parameterise the timeline once the Stone starts reversing things. If Strange reverses an apple while he and the Stone remain outside the reversal, Strange remembers seeing the apple rewind while the apple returns to an earlier physical state. If he reverses a larger region, the matter inside that region is reversed too, including brains, memories and clocks. The people inside therefore do not remember the interval that has been undone, while Strange does.

> The only invariant reference here is the Time Stone itself, because anyone can be the person using it. The user can sit inside or outside the region being reversed, different observers can remember different things, and ordinary clocks can themselves be reversed. The Stone is the object whose experienced ordering remains available as the reference, with each point in that ordering corresponding to one complete matter-and-energy configuration of the universe. In shorthand:

timeline = X(τ_TS)

where X is the complete matter-and-energy configuration of the universe and τ_TS is the ordering observed / experienced by the Time Stone itself.

The closest physics analogy for the deterministic part is superdeterminism, in the sense that the intervention itself is part of the full physical history rather than an independent choice arriving from outside it. The decision to use the Stone, the Stone being used, the rewind and the resulting state are all contained in the same complete history. Changing the past was always determined to happen inside the timeline.

This is only really significant inside that universe/timeline. From the level of the Multiverse, the structure of timelines has not changed (as it was completely determined). The Time Stone reversal was always part of that timeline and was always predetermined within its history. The drawer of useless Infinity Stones at the TVA fits this nicely: the Stones can have enormous control over the physics inside a universe without controlling the higher-level structure that contains the universes.

Summarising before final section:

> Quantum Realm: changing the visited past creates another timeline.

> Time Stone: changing the past was already determined in the timeline; the timeline is the sequence of matter-and-energy configurations ordered by what the Time Stone itself experiences. No branch is created.

---

   

3. Loki and the TVA: meta-time

Quick reminder of the Loki setup: before Loki, He Who Remains used the TVA to maintain the Sacred Timeline, a controlled set of permitted timelines woven mainly around the Earth-616 / Avengers history. Branches were pruned when they led outside the structure he wanted, especially if they could produce rival Kangs. In this framework, that also means no persistent Fantastic Four or X-Men timelines. After Loki Season 2, Loki replaces that pruning regime and allows the branches to grow and persist.

> “Before Loki” and “after Loki” are therefore not dates inside Earth-616. They are two different configurations of the whole branching system, measured at the TVA level.

For an intuitive picture, lay a tree on its side. The trunk is a timeline, left-to-right is ordinary Earth-time, and branches can grow from any point along it. Now stand outside the tree with some shears. You can cut a branch growing from what people inside the timeline call 1200, then one from 2012, then one from 3000. Those are completely different dates in Earth-time, but from your perspective you just performed three actions one after another.

So there are two parameters: position along the tree is local timeline-time; the time experienced by the person manipulating the whole tree is TVA meta-time.

[See Image 3: TVA meta-time diagram]

> That is why “before Loki” and “after Loki” are categorical states of the Multiverse, not sequential dates when viewed from inside a universe. Before Loki, in TVA meta-time, a Fantastic Four timeline is not part of the permitted Multiverse because He Who Remains prunes the branches that would allow that history to persist. After Loki, that timeline can exist with its entire local history intact.

This produces a strange but important consequence: from the perspective of beings living inside Earth-616, the Fantastic Four timeline can be said to have never existed under the “before Loki” configuration, yet to have always existed under the “after Loki” configuration. There is no single Earth-616 date when it suddenly appears. “Before/after” refers to TVA meta-time; “always” refers to local time inside the timeline itself.

One slight lie in the tree analogy: I called the x-axis “Earth-time” because that is the easiest way to picture it. That works only while the Time Stone is not reversing Earth itself. From section 2, the rigorous x-axis is actually the sequence of complete matter-and-energy configurations ordered by what the Time Stone itself observes / experiences, τ_TS.

Marvel also seems to roughly align the “before Loki” era with stories released before Loki in 2021, and the “after Loki” era with the Multiverse-heavy stories that followed. So my best guess is that Endgame still belongs to the old TVA-controlled setup, while No Way Home, Multiverse of Madness, Deadpool & Wolverine, Fantastic Four etc. are being shown to us after the branching Multiverse has been opened.

> Personal Thoughts: I like what Marvel did here because it gives a clean way to reconcile the older movie continuities. Raimi’s Spider-Man and the Amazing Spider-Man films do not need to be rewritten into Earth-616. No Way Home can simply establish that those complete histories exist on other timelines in the same Multiverse. The same logic lets a Fantastic Four universe have its own full history without needing an explanation for why those characters never appeared in Endgame.

Reposting this from my old account

---

   

Summary

The full object is a tree where every timeline path is a predetermined sequence of matter-and-energy configurations, ordered by what the Time Stone itself experiences. Sub-branches can split from any point along any existing path, either naturally or because Quantum Realm time travel changes something.

> This is basically where “free will” sits in the MCU framework. Every individual timeline already has a determined past and future, but an observer living inside it does not know which future branch they are going to move into. From inside the universe, the future still feels open; from the level of the completed timeline tree, every branch already has its own fixed history.

That is the time framework I am using for the rest of the MCU model. The next post I will be making is regarding space: once where universes, realities, branching timelines, dimensions, realms and planes become a containment/connectivity problem rather than another version of “parallel universe”.

---

   

TL;DR

• A timeline, X(τ_TS): a sequence of complete matter-and-energy configurations in the universe, ordered by what is observed / experienced by the Time Stone itself.
• The Time Stone: reverses the physical configuration in the universe while remaining entirely inside one predetermined timeline. No branching occurs.
• Quantum Realm time travel: an intervention can split off a new timeline from a point in that sequence.
• Natural branching: new timelines can split from the sequence without a time traveller causing it.
• The TVA / Loki: operates on the whole tree of timelines from TVA meta-time.
• Free Will: not knowing which branch you will move into

If anyone can think of an MCU example, not comics, that doesn’t fit this, comment the specific scene. Would be cool to see if we can make this properly rigorous together.