This post consists of explanation of the theory backing the fic the grandfather paradox, so beware spoilers? hehe \o/

So, having finished my first story under this alias that actually utilizes theoretical understanding and not just self-indulgent ego , I think some explanations are in order!! \o/ Have some quick fun facts about this fic in the meantime yay hehe:

1. Plot-wise, almost everything was inspired by video games: plot by Life is Strange and Bioshock Infinite and The Vanishing of Ethan Carter, Jaebum and Yugyeom’s father/son dynamics by Papo and Yo, and a lot of the music I used to write this consisted of video game OSTs like To the Moon, and songs from Undertale (rip)
2. There were entire sections regarding Yugyeom’s past/future, with more explanation on how he discovered his ability to turn back time, involving Yerin and Jimin as well as more Yugbam happiness, that I cut out, because it didn’t suit the tone of the chapter :"")

So YAY, now down to actual explanations and stuff that people wanna read!

First, let’s start with a brief crash course on what the grandfather paradox actually is:

“The grandfather paradox is a proposed paradox of time travel which results in an inconsistency through changing the past. The paradox was described as early as 1931, and even then it was described as "the age-old argument of preventing your birth by killing your grandparents”.

The paradox is described as follows: the time traveller goes back in time and kills his grandfather before his grandfather meets his grandmother. As a result, the time traveller is never born. But, if he was never born, then he is unable to travel through time and kill his grandfather, which means the traveller would then be born after all, and so on.”

Doesn’t exactly make sense yet, does it? But then there is more!!

“An equivalent paradox is known (in philosophy) as autoinfanticide, going back in time and killing oneself as a baby.”

So half of it makes sense now, but the other half doesn’t. So let’s have yet another definition of the grandfather paradox!

“Rather than necessarily physically preventing time travel, the action removes any reason for the travel, along with any knowledge that the reason ever existed, thus removing any point in travelling in time in the first place.”

Prepare to be enlightened on a topic that probably won't have any practical use in the remainder of your life!

The Grandfather Paradox exists in two forms in this story: the first, being what Yugyeom mentioned, the idea of going back to kill yourself as a child, hence creating a paradox. Making a quantum leap of logic here, that having a paradox in the timeline would make it self-destruct to avoid the paradox, this would eventually destroy the timeline that decrees that Jinyoung dies in the first place. Imagine a chronological tree branch on the night that Jinyoung died- one saying that he died, and the other saying that he didn’t.

Theoretically, when Yugyeom came back to kill himself before Jinyoung could die, he should’ve destroyed every part of the branch after the crucial point where it decided Jinyoung should die, hence preventing any possibility of Jinyoung dying, in any timeline.

But, as people are concerned, and I did think about this for a really long time while planning this, shouldn’t pre-death six-year-old Yugyeom still be alive? Since teen!Gyeom only destroyed every part of his life after Jinyoung’s death, shouldn’t baby!Gyeom still be with them? And possibly be the only one who vaguely knows, across timelines, that his future self died to save his parents?

This is where the second grandfather paradox comes in. With another leap of logic and assumption, teen!Gyeom is technically the cause of Jinyoung’s death, because if he hadn’t caught the pot to prevent Jinyoung from getting burned, nor had he saved Bambam from cutting his chin on the table, Jinyoung wouldn’t have gone to get the car on that night. But if he removes the possibility of Jinyoung’s death, he removes the possibility of himself existing, and hence the possibility of himself going back to cause Jinyoung’s death, removing the need for him to come back in the first place, hence creating another paradox.

Hence, if we’re operating under the common assumption that having any paradox at all causes the timeline to collapse and self-destruct to avoid it, then we’re going with the theory that by destroying the timeline where Jinyoung died, Yugyeom destroyed every single timeline that involved him meeting and being adopted and raised by Jinyoung and Jaebum.

Long story short, Yugyeom cannot exist as Jinyoung and Jaebum’s son in the same timeline as one where they are both are alive.

The timeline I eventually explore is one of the many in existence- Yugyeom was never abandoned, hence he was never adopted, and Jaebum and Jinyoung adopt Youngjae instead. He remembered that Jaebum and Jinyoung were once his parents, as a child, but because his journal hadn’t been created in this timeline, combined with the displacement trauma of having to deal with the memories of several timelines at once, Yugyeom, upon being rejected by Jaebum, eventually forgets his previous life.

(but then yugbam hehe)

Jaebum, in the second last chapter, rejects Yugyeom, because teen!Gyeom’s presence in his life was what eventually made him question his mentality of “not my business to pry”, and him learning to overcome that personal obstacle was what eventually gave Yugyeom the courage to go through with everything. This, ironically, then erased anything Jaebum learned in the existing timelines, creating a mini-paradox in hindsight.

Yup, so I hope that managed to answer some questions (and not confuse anyone further TnT) I still have messages from some of you guys to reply to cries I'm being flooded with work here sighs. Have a great day guys, and once again, thank you so much for all the support you’ve given to this fic >.< Love you guys <3333