@DrRichards @MyCoolYoung @Synthesis @Nebula @others that want clarity on Endgame time travel

Okay, can finally address time travel in the movie. I spent a lot of time thinking about this last night, confused myself and had to sleep on it, and have finally (I think) made sense of everything. All I'll say is time travel is hard, its a tough concept to really understand, and if you think about it for a while and start to analyze everything, your mind begins to jump down a rabbit hole of confusion. BUT there is a light, there is clarity at the end of this rabbit hole, and time travel can be properly understood once you get past the confusion AND if the rules established aren't broken and are followed through (which, in the case of the Endgame is true).

There are a variety of articles and videos out there attempting to explain time travel in the movie, but the only one that I've seen gets it pretty much correct to me (and does a really great job at explaining it) is this article:
https://screenrant.com/avengers-endgame-time-travel-explained/

I recommend reading through that after this comment, and I will let the article do most of the explaining, but here are the really important points: 1) the infinity stones are returned to the past, preventing alternate realities from occurring, 2) Thanos 2014 and his forces coming to 2023 creates a parallel alternate timeline for 2014, 3) old Cap living in the past always happened. I will flesh these out below so they make sense (sorry if its long).

1)
So, Bruce Banner and the Ancient One provide some really important info for how time travel works, and these rules are followed WHEN talking about the Infinity Stones. As the Ancient One explains, the infinity stones are fundamental to the flow of time. You can take a baseball mitt from the past and not interrupt time (this trivial scene in hindsight is important in explaining the rules), but you can't take the stones from the past and not return them; not returning them would create breaks in the reality of space-time.

This is why Cap goes back in time to return the stones to right after from where they were plucked so that the timeline remains intact. Returning the stones closes/prevents any splits (alternate timelines/realities) that would arise from plucking the stones from the past. Sure, one could question how Cap would address the space stone no longer being housed in the tesseract, for example, but you've got to imagine that this is properly accounted for in the movie and that everything is returned how it is supposed to be/originally was; plus, with the time stone or even reality stone, he could fix this (if Strange told him how to do so).

Everything that happened when the Avengers go to the past (Howard meeting Tony, Cap stealing Pym particles [which also explains how he was able to go to live with Peggy, cause he had extra Pym particles to use], the Ancient One talking with Bruce, all the Cap stuff in 2012 [Hail Hydra, fighting himself, etc.], Thor talking with his mom, Nat sacrificing herself, etc.) was always supposed to happen, we just never saw it happen until now. Even Quill getting knocked unconscious was supposed to happen I guess, but what comes AFTER Morag is alternate (see point 2 below).

The one break in time with a stone that isn't resolved in the movie is Loki escaping with the tesseract in 2012. But this was obviously intentional, and will be resolved in the Disney+ series. But he has to return to right after he disappears in 2012 by the end of his series in order for the timeline to remain intact.

2)
While returning the stones (and mjolnir) to the past where they belong closes breaks caused by their absence, and the timeline remains in tact with no new alternate realities, the same cannot be said for non-infinity stone things being plucked from time. Thanos and his ship coming to the future from the past creates an alternate reality (but not one that would disrupt the fabric of spacetime like a stone being taken from the past and brought to the future and never being returned). This is why Nebula can shoot this alternate, younger version of herself and still survive. And its why Thanos and his forces can be erased from 2023. It doesn't undo the events of the past (something that is clearly explained by Banner early on) from the main/original timeline, those events already happen. But there is now an alternate timeline/reality in 2014, parallel to the original timeline, in which the infinity quest ends in 2014, the Guardians never form, etc.


This alternate timeline that runs parallel to the MCU perfectly falls in line with the concept of the multiverse, something that has been brought up a few times in the MCU. And the best way to understand this alternate reality is to think about Agents of SHIELD S5. In the alternate reality of the quaked apart future, Flint goes about rebuilding Earth, even though the Agents prevent the destruction from happening in the present. Likewise, everything that happened up to 2023 in the MCU still happens, but there is an alternate reality now where Thanos dies in 2014.

3)
Cap always lived in the past, we the audience just weren't aware of this until now. It is not an alternate reality situation like Thanos jumping from 2014 to 2023. Cap lived in the past with him and Peggy keeping and hiding the world's greatest secret. What's been established already in the MCU, especially with Peggy, allows this, nothing is voided. Cap returns to some time after Agent Carter S2 (there was no indication of what year he was wit her, it was late 40s, early 50s based on vehicles) and lives out the rest of his life, being the family man and not the hero and thereby letting the timeline play out as it should.


Now, how does Cap still have an intact shield to give to Falcon? Well, I think there is actually an explanation from Winter Soldier. If you watch that, it seems that there are two shields, one painted with stealth colors (known as the Stealth Shield) and one painted vibrant red white and blue (the classic Shield). Perhaps he picked up the stealth shield from wherever it was in storage (guessing the Avengers HQ) and gave it a new paint job for Sam. We know that after 1991, Klaue steals and begins to distribute vibranium. It could very well be that Tony retrieved vibranium from Klaue (we know he used to attend the same conferences as Klaue) and makes a second shield.

At least that's my theory, that could be wrong about there being two shields. Either that or he was able to get T'Challa to make a second one after they defeat Thanos but before they send 'present day' Cap to the past. Either way, the timeline is still intact.



Okay, I think I've explained everything :-) Does this make sense to you guys?