Science Tuesdays - A Look at World Line Travelling

This was a post I wanted to do for a while, seeing as this week and the next I have much more free time, I decided to do some more rant posts that I haven't done in a while. They did a good job explaining how the time travel worked and it was pretty much seamless but with any other established rules, the own writers break them creating plot holes. I like it when they explain how things work, but it takes solid writing to make sure you follow your own universe's rules.

Nice simplified illustration of how their world works in a nutshell

So first I'll recap the 3 main rules they explain about time travel within their world:
1. The only one that can perceive the change in timelines is Ookarin with the skill he named Reading Steiner.
2. The world lines branch out due to cause and effect to create an infinite number of parallel universe. Pretty much exactly the same principal of this world and this theory.
3. Cause and effect play a much more extreme roll in this theory of time, their are events that can not be altered. A cause so powerful that the effect can not be changed even after introducing new elements. The attractor field as they called it.

These are the 3 things set as almost rules to this world as they are clearly explained to you, axioms for this universe as I like to call it. I'll also assume that canceling a Dmail is possible! (Cancelling it 100% should be impossible btw)

So with those setup, time to breakdown the time traveling bits within this anime:

So we start the anime at the beta worldline which quickly moves to the alpha line when Ookarin first sends the text message of Kurisu's death; The one that started it all and the anime ends with. We then enter four successive D-mails that are ordered: Moeka, Ruka, Feyris and Suzu. All the time shifts was just variations of this Alpha timeline. Their picture of how their "time looks" is pretty accurate to their system. Multiple huge branches out denoting the major timelines that are extremely different with many small branches among them to show small variations. Much like a tree, the small branches is what those Dmails moved between instead of moving a big branch away. (Hope that makes sense D:)

This image of how time works in their world is very well explained with the picture they used which is vastly different from how the infinite parallel universe map would look like. This is purely because of rule 3 that forces events to occur. With some more technically stuff out of the way, time to look at the problems with their time traveling.

I'll start easy, Reading Steiner. It was pretty simple to see random people all started gaining memories back to better help the plot flow. Coincidentally, it was always the one that sent the D-mail and had their life altered the most that remembered. The problem with this is that everyone should remember things in inner loops of the Dmailing chain. So Moeka would retain memories of original world and for every other instance. Ruka would the remember Moeka's line, the changed one, Feyris and Suzu. Feyris would remember Ruka's, her own and Suzu's timelines. This is because the Dmails are done after the preceding Dmail causing a branch within a branch. Theoretically, they should also retain these memories, but they don't.
This same theory could also explain Reading Steiner, he caused a jump in time lines once and now any branch off of this makes it so he is unaffected and can remember it all, just a side theory.

So I'll bunch the second and third rule together as they are pretty much tied together. The attractor field created branches or different main timelines since the certain events would be destined to occur. This also means that the timeline they are in has a predestined future regardless of the actions he takes. Now the problem revolves around the magical Metal Upa. In the final episodes, it is portrayed that he needs to recreate the loop that he witnessed due to the attractor field. This is where things get messy, I have to split next section based on the two possibilities. The first possibility would be this specific Ookarin is the only one with Reading Steiner and the second possibility would be every Ookarin had this ability.

The first possibility means that after the Ookarin sends the first D-mail, he will have no recollection of the memory and time travel will not be successfully created by the lab, thus leading to SERN creating dystopia. He would need to be able to perceive the change in timelines to be able to tell that time travel was created successfully or at least advance it faster. This also leads to him not questioning Kurisu about her death, so she would never even join the lab. This presumption is obvious turned false since the "main" Ookarin claims that his other self is in for 3 rough weeks implying he would be walking the same path he took.

The second presumption is further shown to be the better one since Suzu from a different timeline can say that only Ookarin had this ability meaning the other timeline's Ookarin had it too. So this implies that the other Ookarin would be redoing everything he has done. This is needed to create the same loop, the problem was something was altered. The Metal Upa was swapped for a green one. That would already imply that once the "other" Ookarin finished undoing all the D-mails, he would be at a different point then the "main" Ookarin. This new Ookarin would only need to stop Kurisu's death without worrying about the academic papers. (I won't even question the logic of how the papers aren't part of the attractor field since it seems pretty staple to this timeline) Either way, this already brings Ookarin to a world where world war 3 is not a threat so their would be no reason for Suzu to come back in time leaving Kurisu destined to die. This "incomplete" loop would be impossible because it creates a paradox. It is now impossible to create world war 3 in any timeline the second the Metal Upa was removed making the message he received and Suzu's existence impossible.

Aside from theses problems, their were other obvious inconsistencies. Why was such radical changes that Feyris and Ruka made not effect much more then one thing. More things should have been changed with their D-mail to the point that meeting again could only be the work of an attractor field.

Why is SERN not in issue in the most recent timeline? That same D-mail would be sent the second the "other" Ookarin sent it and would have triggered the detection from them. They would still be facing the same issue they had with the beta timeline.

The new timeline they carved out without world war 3 and dystopia is impossible. The motion of SERN trying to build a time machine is already in place. War for that control will happen regardless, unless the root cause, SERN's existence, is removed. I like how they glazed over that like this timeline will be all peachy now.

The true world line being whichever one the "main" Ookarin is in conflicts with the earlier possibilities that every Ookarin possesses reading steiner. That would imply every Ookarin would have to eventually converge back to his line which is already impossible as some are obviously stranded. This statement of a main world line is wrong. What is the true world line is in the eye of the beholder. All the threads of worlds still exist regardless if this version of Ookarin is in it. To another version of himself, he thinks his line is real too. This just means no timeline will ever be considered the true one, only a best possible outcome which would exist whether or not the "main" Ookarin found it, thus making his quest meaningless.

The plot was just filled with holes all sprung by that final conclusion. The attractor field was just written as a way to keep the plot intact but is also the sole reason the plot holes come out. To create this seamlessly with this device is impossible just due to how it's existence is impossible within the parallel world theory. I think I rambled on long enough and that is a whole topic on it's own though so I'll leave it at that.