Timeline theories: which one do you like best?

[rereboy]

For a long time, I've had my own theory about how the time travel and the timelines from the Cell arc work, and I've pointed it out in various topics on this forum over the years, even though I never actually created a topic of my own about it, I believe.

However, recently, I've noticed that there's another way to make sense of the timeline and time travel business. But I'm not sure if it's any better than the old one. It has some advantages, but it also has some disadvantages.

So, I figured I would create this topic explaining my thought process on how this all works to see what you guys think, and also to discuss these themes if you are interested.

There's already other topics about timelines and time travel in the forum but I thought it would be relevant to create another topic since I'm interested in seeing which theory of mine is more agreeable with you guys. Hope that's ok.

Also, beware, this will be a fairly loooong post

So, for starters, I will begin to explain my old theory:

Theory 1

It all began with one single timeline.



In this unaltered timeline, after Freeza and Cold are defeated by Goku, Goku falls ill and dies. Shortly after, the androids attack. And thus is born the world that Future Trunks knows.

In this world, of all the fighters only Gohan is left, as well as Trunks, but even Gohan eventually dies fighting the androids. Alone, no matter how much he tries, Trunks finds that he is not a match for the androids either.

What to do?

Enter Bulma and her amazing boo... er, brain. That's right, when muscles failed, Bulma and her intellect saved the day by creating a time machine (one would think that it would be easier to create a super-weapon capable of destroying the androids than a time machine but, hey, I won't argue with genius).

Bulma gives the time machine to Trunks and he uses it to travel back to the past.

This is where we first encounter the time travel mechanics in Dragon Ball, which we will have to analyze properly to make sense of them.

There are several theories in (science) fiction regarding what would happen in a time travel scenario where a time traveler changes the past. They range from the complete destruction of the universe (the fear of the Doc in Back to the Future), to the destruction of the old timeline, to the creating of parallel timelines.

Which is the case in Dragon Ball?

As we can see in the manga, the universe didn't end and Future Trunks and his own timeline (future) continued to exist since he returns to it. Therefore, it's clear that Dragon Ball adopted a parallel timelines approach to time travel. And thus, Trunks, with his time travel, creates a new timeline, changed from his original timeline. His own, original timeline remain, and a duplicate, with the changes introduced by Trunks is born.



What are the differences in this timeline compared to the old? Trunks killed Freeza and Cold and gave Goku his medicine and that changed the timeline from that point on.

We also know that Trunks returned to his timeline after saving Goku. So, we can wonder, did that time travel create yet another timeline?

To answer this question, we have to dwell a little deeper on time travel mechanics.

As I've said, there's various theories in science fiction about what would happen. But why do these theories exist? What problem are they exactly answering?

They are answering to the unique problem caused by time travel: a paradox.

The problem can be described with the following: if a man travels to the past, and kills his past self, he is not only killing a person, he is killing the person that would grow to be him. But, if the person that was going to be him, is killed, then how can he exist? And if he doesn't exist, how can his past self have been killed by him? And if his past self couldn't have been killed, then he would eventually become his future self and would kill his young self. And if his young self was killed, then, once again, how does he exist?

This is a never ending logical problem, a paradox, that exists uniquely in a time travel scenario. And that's why those theories exist: to offer a logical solution to the problem.

Therefore the chosen solution applies to whenever this problem, a paradox emerges. By traveling to the past, Trunks created a paradox, which is why a new timeline emerged.

But did his journey back to his timeline create a paradox? I don't think so. He presumably traveled to a moment in time after he had traveled back, so, therefore, there wouldn't be any paradox.

And what about his journey back to the past? Here we have to consider carefully what happened.

If we pay attention, it's clear that Trunks, unlike with his first journey, didn't travel to the past of his own timeline. If he did, he would just travel back to a point in time where Goku had already died and just before everybody was about to get surprised by the androids, which was what happened in the past of his timeline, and another paradox would have been created alongside another timeline.

Instead, Trunks arrived in the timeline that he had created. What does this mean?

Imo, this means that the time machine is not only capable of time traveling, it's also able to travel to a point in time in the timelines previously created by the machine. That's how it can go back to that timeline and not to the past of the original timeline. And does this create a paradox? Imo, no, because, at this point, the timeline was already separate from the original timeline. These journeys are no more than journeys that don't create a paradox and thus no timeline is born from them.



But, is this timeline 2 the timeline that we see in the manga? The main timeline?

As we see in the manga, the main timeline had a Future version of Cell that had time traveled. What does this mean?

Well, as we saw, Dragon Ball adopted a parallel timeline approach. Which means that every time a timeline is changed by a time traveler, there will be an original timeline and duplicate of that timeline with the changes introduced by the time traveler. But the main timeline, the timeline of the manga, has the intervention of both Trunks and Cell. What does it mean? Well it means that this timeline can't be the main timeline. This timeline only has one intervention, and there's no Cell intervention. This will become clearer in a few paragraphs. For now, let's continue with the analysis.

So, without the intervention of Cell, how would things play out? It's unknown. And being unknown, we have to to consider the possibilities and imagine. The gang either managed to beat the androids or they didn't. Let's assume that they did. What would happen?

Well, Trunks would then return home and get rid of the androids the same way that they managed to get rid of them in this timeline 2. And then what?



Enter Cell.

So far no one had heard of Cell. But now, after long years growing, Cell awakens in Future Trunks' timeline. Trunks never found out about him because he hadn't appeared in his timeline yet and the timeline 2 didn't have the intervention of Cell. And Cell doesn't find the androids because they had been defeated. Instead he finds Trunks. So, Trunks being surprised by Cell, what happens? Cell either defeats him or Trunks defeats him. Which one happened?

Well, so far, this scenario seems awfully similar to what Cell in the main timeline described... It seems to fit... What does it mean?

It means that the scenario we imagined is correct.

In all likelihood, the gang did manage to beat the androids (perhaps by managing to create a remote?) and Trunks returned home to his timeline.

Then Cell woke up and defeated Trunks. After defeating Trunks, Cell uses his time machine at random and the machine travels to the timeline it has created (timeline 2) but, this time, this time travels creates a paradox because Cell's intervention will change things and disturb the logical flow of events because Cell traveled far into the past and so, his journey, created a new parallel timeline.



Timeline 3 is born.

And is this timeline the main timeline? It's a timeline with both the intervention of Trunks and Cell and their changes, so, yes. This is the main timeline, the timeline from the manga.

However, one important question arises here. And is perhaps the most complex regarding the time traveling mechanisms. The question is the following: in the timeline 3 we also have a Trunks arriving from the future to help the gang against the androids. But wasn't he in timeline 2? How can he be both in timeline 2 and 3? What is going on?

To answer this, we have to wonder on exactly happens when a timeline is duplicated. What happens? Well, like the term says, there's a duplication. Suddenly, there's two time lines, not one, and two earths, two universes, two Gokus, two Kamis, two everything.

But, this is not simply a physical duplication. A whole timeline was duplicated.

That means that not only a past but also also a future was duplicated. Timeline 3 has a past, which is not the past of Timeline 2. It's exactly the same in terms of event, but it's not the same one. To put it simply, in both pasts there's a Bardock who does exactly the same, but there's one for each timelines (two Bardocks).

And what about the future? Does the same thing happen?

The answer is yes. Everything that was going to happen, happens. The only difference is that the new timeline will have the added differences introduced by the time travelers on top of everything that was going to happen, influencing it.

What does it all mean? It means that Trunks that existed in Timeline 2 is also duplicated in Timeline 3. Just like every other event and character from that timeline was duplicated from timeline 2, he is also duplicated. Just like them, he appears out of the paradox. He is no exception.



Confusing? I admit it's a bit, but I honestly think it makes complete sense in light of what happens in the manga.

So, moving on, now we have timeline 3, the main timeline, with the presence of Trunks there explained.

The events in this timeline we are all well aware. Cell is defeated by Gohan, and Trunks returns home.

It's interesting to note that this Trunks is the one duplicated. So, we could wonder, could he return to timeline 1? Well, his time machine is duplicated and is exactly the same. That means that it can time travel but it can also return to the timelines it created and to the original timeline, like it had a set of coordinates. So, imo, there is no reason why he shouldn't be able to and that's indeed what happens, when we see him returning to the original timeline.

However, this return disrupts the logical flow of events since he returns to a point in time before Cell, who they had killed, had time traveled. Therefore, this timeline creates a paradox, and a new timeline is born: timeline 4.



We see the events of this timeline. Trunks, now being much stronger, defeats the androids and Cell easily.

Also, you can wonder, isn't there supposed to be another Trunks in this timeline? A duplicate from the one that returned from Timeline 2, since timeline will be a replica of Timeline 1? And you would be correct. Indeed, there should be another Trunks here. However, there's an unique problem here: they both had the same exact machine and they both probably returned to the same exact location and time. So... What would happen? I can only see two possibilities, since they can't both exist in the same location at the same time: they would either both be destroyed or one would override the other. Given what happens in the manga, where there is only one Trunks, it seems that the duplicate was simply overwritten.

This was my original theory. Here are the advantages and disadvantages of it:

- Advantages:
It closely follows the manga with the minimum amount of assumptions regarding unseen events that I could come up with. The assumptions and theories are mainly about the mechanics of how it works, not actual events in the manga.

- Disadvantages:
It requires of us to disregard the fact that Cell stated that Freeza and Cold were killed by Trunks in his timeline instead of Goku. That is treated as a plothole, just like when Trunks tells Goku that the androids were named #19 and #20, instead of #17 and #18 like he does later.




So, like I said, for a long time, this was my theory. However, recently I came up with this one:

Theory 2

Everything about the mechanisms of time travel and timelines works the same in this theory. There's no change regarding that.

So, at first we have one timeline.



Then the androids appear, and eventually Trunks time travels, which creates timeline 2 (following the explained mechanisms).



We also have the travels of Trunks, which don't create a paradox.



And once again, we are faced with the question: what happens in this timeline, without Cell's intervention? And this is where the theory is different.

On the first theory, as mentioned, I reached the conclusion that they defeated the androids somehow, going by what Cell eventually said. But what if something else happened?

What if they didn't manage to beat the androids? What if in this timeline, they still fail to stop the androids, and the future of the timeline is strikingly similar to the future of timeline 1? After all, a lot of things could have happened without the interference of Cell.

We have to go on some assumptions here regarding the events, but lets do it and see where it takes us.

What if they lost?

What if Piccolo, Goku, Vegeta and Future Trunks (and perhaps the others, except present/baby Trunks) died fighting off #17, #18 and #16, and of the androids only #16 dies, while the other two androids survive?

It's certainly possible... #16 was very powerful, and Piccolo, the strongest one, might not even win against #17 alone as we saw in the manga. If they faced off against the androids or the androids forced them to fight before they went to ROSAT, this scenario could have happened, and the fight might even have happened in the look-out if the androids went to look for them there (for example after defeating Piccolo and realizing that Kami had something to do with Piccolo's power, and thus deciding to look for Goku there, before they went into the ROSAT, and the ROSAT and the temple being destroyed in the fight).

So, let's assume this scenario happens. What do we get? Well, we get a scenario close to the one on Timeline 1. #17 and #18 would still be alive and even Future Trunks would have died. Only baby Trunks would be left.

And after some years had gone by?

Well, there's no reason to assume that after a while the androids wouldn't be as bad as the ones in the original timeline out of boredom, so the world would probably be in ruins, pretty much like the original timeline. Bulma would have known about the time machine and if Trunks' time machine had been destroyed with him (he kept it in his pocket) she would have to build one from scratch. After some years she would have done it, just like the one from the original timeline had done.

So, suddenly, the scenario becomes even closer to the original timeline. Extremely close in fact. However, there's some differences. This Bulma would know more about the androids than the bulma in the original timeline, and she also would know that time travel is not a guarantee that everything will work out. So, it makes sense that she and Trunks would have tried other things.

What if, those others things, like, for example, attempting to build a remote to shut the androids down worked?

Then, they would have defeated the androids and they would still have a time machine.

But, despite having defeated the androids, they would still have a need to use the time machine since, despite being aware that it wouldn't change much for them, they could create a timeline where their friends were alive and had defeated the androids without a problem.

So, let's imagine that they plan to use the time machine to create that timeline, and even set the timeline to a time even significantly before Freeza and Cold had arrived, so that their friends have even more warning (better safe than sorry).

Enter Cell.

Finally awake, he doesn't find the androids, and he kills Trunks (who wasn't very powerful in this timeline), and he time travels creating timeline 3.



As you can see, the difference in this theory is that Cell is not from Future Trunks' timeline and the Trunks he kills is not Future Trunks. He's from Timeline 2, that ended up being pretty similar to timeline 1 and where Trunks also ended up very similar to Future Trunks.

This fits with what Cell tells us and explains why Trunks was the one that killed Freeza and Cold in his timeline. It's no longer a plothole, it also makes sense and is explained since Future Trunks killed Freeza and Cold in Timeline 2, indeed.

What Cell told us of his timeline is very little so it can easily mean either the original timeline or one similar to it. In this case, it would be Timeline 2, which ended up being similar to the original by chance.

As for timeline 3, it's the main timeline, just like it was explained in the first theory. Everything happens like in the manga. Cell never gets to grow up because he is killed in Cell's lab and Future Trunks is there because he is duplicated from timeline 2 like I explained in theory 1, and the adult Cell is defeated by Gohan.

Then, Future Trunks, travels back to the original timeline and now, since Cell wasn't the one from his timeline, there is no paradox. He simply arrives at timeline 1 and kills the androids and Cell from that timeline with his power.



This was my new theory. These are the advantages and disadvantages:

Advantages: it explains why Cell said it was Trunks who killed Freeza, and it might even offer a more plausible explanation for why the time machine was set to such an early date. Thus, it contains no plotholes that I can see. Also, it allows the theory to be less complex because it only requires 3 timelines.

Disadvantages: it requires more assumptions regarding events in timeline 2. I don't think they are stretch but it definitely requires more than my first theory.


Conclusion: I'm not sure which one I prefer, but right now I'm more inclined towards the second one. What do you guys think? Thanks for the patience in reading

Btw, if anyone else has come up with the same theories, I assure you I'm not stealing credit, I just must have missed it



EDIT:

Victorious mentioned something that I forgot to explain. His question was the following:

Lets look at your second theory. You think Future Trunks created Cell's timeline, and Cell created the main timeline? How do you explain the multiple times Future Trunks travels back and forth between the main timeline and his timeline, which according to you is the original? My question is in the main timeline, which for you is timeline 3, when Future Trunks kills Freeza and gives Goku the medicine where does he go? He must go back to timeline 1. But if he's just a duplicate then he'd be going back to the same timeline that the original Future Trunks who killed Freeza in Cell's timeline came from and travelled back and forth to, right? Meaning you'd get two adult Trunks in timeline 1. Which definitely never happened.

My answer is the following:

The situation is covered by the way I described how the mechanics work, especially regarding the creation of timeline 4 on the first theory. And it happens in both theories, it's not just an issue of the second theory.

Let's analyze it step by step.

Like I said, Cell creates Timeline 3.

This causes a duplication of Timeline 2, with the added changes brought on by Cell.

Following what I explained about the duplication, this also duplicates Future Trunks. So, Future Trunks appears on this Timeline and, for a brief period, he goes away. Where does he go?

As explained, his time machine can freely go back to the original timeline (as well as the timelines it created) and the machine that this duplicate Trunks has is exactly the same as the one in Timeline 2 has.

Also, so far, this Trunks is exactly the same as Trunks in Timeline 2 because Cell hasn't influenced anything yet.

So, when he goes back, he goes back to timeline 1.

And there is the heart of the issue. This Trunks, because he is exactly the same as Future Trunks, goes back to exactly the same point in time and location that Future Trunks also goes to when he returns after saving Goku.

It's the same kind of situation as when, in theory 1, when Timeline 4 is created, Trunks returns after Cell is defeated to the same point in Timeline 1 where another Trunks also returns.

At the time, I said that I could only think of two possibilities, since they can't occupy both the same place at the same time. They would either both die, or one would overwrite the other.

Imo, in theory 1, one overwrote the other and created a paradox and timeline 4.

This situation is the same in that regard so, Imo, one Trunks also overwrites the other in that situation.

However, now we have to wonder, does this create a paradox like it did regarding the creation of timeline 4?

Imo, apparently no, because, unlike the situation in timeline 4, both Trunks are exactly the same, in mind, body, and knowledge.

What created the paradox in timeline 4 was the fact that one Trunks was different and that would change the logical flow of events. But in this case, both Trunks will do exactly the same because they are exactly the same. Thus, one overwrites the other but there is no paradox, and no new timeline.

However, we can also wonder, now that there has been this overwriting, the remaining Trunks travels back to timeline 2 or to timeline 3?

It's on this point that there might be some justification for a paradox.

If Trunks went to Timeline 2, he would continue to overwrite the other Future Trunks and nothing would change.

But if he went to Timeline 3, he would overwrite the other Trunks there, but the situation would cause Future Trunks to not appear a second time on Timeline 2 since that Trunks wasn't a duplication. Causing a paradox.

So, if the situation is the last one described, there could be justification for a paradox to be created when that Trunks travels to Timeline 1, and a new Timeline.

How do we know which situation is true?

Well, we will have to take a very close look at how the machine works.

As it was said, the machine is capable of going back to its original timeline. That means that it can identify it, like with a set of coordinates in the space-time continuum or something (ask Dr Who for more details).

And it can also go back to a timeline it has created.

However, when it's a duplicated time machince that tries to go back to a timeline it (thinks) created, does it go back to the duplicated timeline thinking that that's the one it created (timeline 3) or does it go to the actual timeline that the original time machine created (timeline 2)?

I think... that both are possible. It really just depends on how exactly the machine works. If, for example, it follows something like coordinates, which are set in the machine just before it creates the Timeline, then the duplicate would go back to the timeline created by the original time machine. If it sets the coordinates after arriving, then it would go to the duplicated timeline.

Either is possible and I don't think any is more likely than the other. For simplicity's sake I'm going to assume that it goes back to the timeline created by the original because it duplicates the coordinates.

That means that Trunks continues to overwrite the one in Timeline 2, and that in Timeline 3, the one that appears just before the androids is a duplicate (that wasn't overwritten).

However, if we follow this assumption, this means that Trunks won't be able to get back to Timeline 3 after leaving it. Which is sad but it also explains why we never saw him again

In short, here's how it looks in the charts:

Theory 1:



Theory 2:

[Victorious]

Lets look at your second theory. You think Future Trunks created Cell's timeline, and Cell created the main timeline? How do you explain the multiple times Future Trunks travels back and forth between the main timeline and his timeline, which according to you is the original? My question is in the main timeline, which for you is timeline 3, when Future Trunks kills Freeza and gives Goku the medicine where does he go? He must go back to timeline 1. But if he's just a duplicate then he'd be going back to the same timeline that the original Future Trunks who killed Freeza in Cell's timeline came from and travelled back and forth to, right? Meaning you'd get two adult Trunks in timeline 1. Which definitely never happened.

[dbgtFO]

Conclusion: I'm not sure which one I prefer, but right now I'm more inclined towards the second one. What do you guys think? Thanks for the patience in reading

Btw, if anyone else has come up with the same theories, I assure you I'm not stealing credit, I just must have missed it

Very well done! Like I said in that other thread to Victorious, Cell's interference is ironically, what ends up giving the characters happy endings, instead of actually bringing doom and gloom like he'd hoped to.

Lets look at your second theory. You think Future Trunks created Cell's timeline, and Cell created the main timeline? How do you explain the multiple times Future Trunks travels back and forth between the main timeline and his timeline, which according to you is the original? My question is in the main timeline, which for you is timeline 3, when Future Trunks kills Freeza and gives Goku the medicine where does he go? He must go back to timeline 1. But if he's just a duplicate then he'd be going back to the same timeline that the original Future Trunks who killed Freeza in Cell's timeline came from and travelled back and forth to, right? Meaning you'd get two adult Trunks in timeline 1. Which definitely never happened.

Yeah, that's a problem.
Rereboy didn't address this over in the other thread, but I had a solution for this problem.
Instead of saying timeline creation are results of paradoxes, they are just created because you can't insert yourself in a time, that has already happened.
Dupli-Future Trunks' attempt to return to the original timeline, like the original Future Trunks himself did after disposing of Freeza and Cold, thus creates the 4th and final timeline, as the time D-FT tries to return to(Age 784) had already passed in the original timeline, where it's now Age 785+.

...Of course it means we have a Cell in the original timeline still being very much alive, but probably unable to become perfect, as Trunks and his time-machine were destroyed in timeline 2.
Maybe Cell could have his own crazy adventures in that timeline Or maybe Bulma finally comes up with a superweapon to take him out or some super powered suit to fight him, shit we could even have it be Mr. Satan, who gets to be the one that takes out Cell in this speculative super suit, then he really does save the world

[Victorious]

Well Cell's travel may have been the reason we get a happy ending, i'd bet he'd take a fate where he achieves his Perfect form and experiences it's power and dies gloriously in battle over a fate where he just lives a long life in his first form. He could have ruled over a world of weaklings and beyong in his timeline, but for him this was no life. He was made to seek out the ultimate power his Perfect form and then to only battle the strongest fighters in history from there. Like he said he's got too much of Goku, Vegeta, and Piccolo in him.

[rereboy]

Lets look at your second theory. You think Future Trunks created Cell's timeline, and Cell created the main timeline? How do you explain the multiple times Future Trunks travels back and forth between the main timeline and his timeline, which according to you is the original? My question is in the main timeline, which for you is timeline 3, when Future Trunks kills Freeza and gives Goku the medicine where does he go? He must go back to timeline 1. But if he's just a duplicate then he'd be going back to the same timeline that the original Future Trunks who killed Freeza in Cell's timeline came from and travelled back and forth to, right? Meaning you'd get two adult Trunks in timeline 1. Which definitely never happened.

Ah, I forgot to talk about that. Or at least I didn't explain properly.

The situation is covered by the way I described how the mechanics work, especially regarding the creation of timeline 4 on the first theory. And it happens in both theories, it's not just an issue of the second theory.

Let's analyze it step by step.

Like I said, Cell creates Timeline 3.

This causes a duplication of Timeline 2, with the added changes brought on by Cell.

Following what I explained about the duplication, this also duplicates Future Trunks. So, Future Trunks appears on this Timeline and, for a brief period, he goes away. Where does he go?

As explained, his time machine can freely go back to the original timeline (as well as the timelines it created) and the machine that this duplicate Trunks has is exactly the same as the one in Timeline 2 has.

Also, so far, this Trunks is exactly the same as Trunks in Timeline 2 because Cell hasn't influenced anything yet.

So, when he goes back, he goes back to timeline 1.

And there is the heart of the issue. This Trunks, because he is exactly the same as Future Trunks, goes back to exactly the same point in time and location that Future Trunks also goes to when he returns after saving Goku.

It's the same kind of situation as when, in theory 1, when Timeline 4 is created, Trunks returns after Cell is defeated to the same point in Timeline 1 where another Trunks also returns.

At the time, I said that I could only think of two possibilities, since they can't occupy both the same place at the same time. They would either both die, or one would overwrite the other.

Imo, in theory 1, one overwrote the other and created a paradox and timeline 4.

This situation is the same in that regard so, Imo, one Trunks also overwrites the other in that situation.

However, now we have to wonder, does this create a paradox like it did regarding the creation of timeline 4?

Imo, apparently no, because, unlike the situation in timeline 4, both Trunks are exactly the same, in mind, body, and knowledge.

What created the paradox in timeline 4 was the fact that one Trunks was different and that would change the logical flow of events. But in this case, both Trunks will do exactly the same because they are exactly the same. Thus, one overwrites the other but there is no paradox, and no new timeline.

However, we can also wonder, now that there has been this overwriting, the remaining Trunks travels back to timeline 2 or to timeline 3?

It's on this point that there might be some justification for a paradox.

If Trunks went to Timeline 2, he would continue to overwrite the other Future Trunks and nothing would change.

But if he went to Timeline 3, he would overwrite the other Trunks there, but the situation would cause Future Trunks to not appear a second time on Timeline 2 since that Trunks wasn't a duplication. Causing a paradox.

So, if the situation is the last one described, there could be justification for a paradox to be created when that Trunks travels to Timeline 1, and a new Timeline.

How do we know which situation is true?

Well, we will have to take a very close look at how the machine works.

As it was said, the machine is capable of going back to its original timeline. That means that it can identify it, like with a set of coordinates in the space-time continuum or something (ask Dr Who for more details).

And it can also go back to a timeline it has created.

However, when it's a duplicated time machince that tries to go back to a timeline it (thinks) created, does it go back to the duplicated timeline thinking that that's the one it created (timeline 3) or does it go to the actual timeline that the original time machine created (timeline 2)?

I think... that both are possible. It really just depends on how exactly the machine works. If, for example, it follows something like coordinates, which are set in the machine just before it creates the Timeline, then the duplicate would go back to the timeline created by the original time machine. If it sets the coordinates after arriving, then it would go to the duplicated timeline.

Either is possible and I don't think any is more likely than the other. For simplicity's sake I'm going to assume that it goes back to the timeline created by the original because it duplicates the coordinates.

That means that Trunks continues to overwrite the one in Timeline 2, and that in Timeline 3, the one that appears just before the androids is a duplicate (that wasn't overwritten).

However, if we follow this assumption, this means that Trunks won't be able to get back to Timeline 3 after leaving it. Which is sad but it also explains why we never saw him again

In short, here's how it looks in the charts:

Theory 1:



Theory 2:



Hope that has answered your question

I will edit the op to include this information.

Instead of saying timeline creation are results of paradoxes, they are just created because you can't insert yourself in a time, that has already happened.

I think that's basically the same thing as paradoxes. Paradoxes happen because the time that the time traveler tries to enter has already happened relative to him. In other words, the chain of events going from the point that he is trying to enter will lead eventually to him and by entering it he is changing what would lead to him.

The thing where we seem to disagree is on the "relative" part. To me, even if something is on Age 9000, that can be the past of someone that is on age 8000 because he time traveled. Time is relative in that way.

Anyway, guys, which one of the theories you prefer?

[TheDevilsCorpse]

I can't buy into it. I can understand the timelines being copied over in full (past, present and future), but time is generally accepted to be fluid. The future being copied over should be nothing more than a filler template that's easy to overwrite due to the actions of the time traveler. In the series, Cell traveling back and doing pretty much nothing but redevelop into his imperfect state causes Trunks to wonder how history changed so much. The idea of Future Trunks being copied over into new timelines may exist in those timelines as a concept in the templates, but regardless of how little has changed, history isn't the same moving forward. Those ripples should distort the future and there won't be a separate Trunks to actually arrive at those points in time to prevent it from being overwritten.

[rereboy]

I can't buy into it. I can understand the timelines being copied over in full (past, present and future), but time is generally accepted to be fluid. The future being copied over should be nothing more than a filler template that's easy to overwrite due to the actions of the time traveler. In the series, Cell traveling back and doing pretty much nothing but redevelop into his imperfect state causes Trunks to wonder how history changed so much. The idea of Future Trunks being copied over into new timelines may exist in those timelines as a concept in the templates, but regardless of how little has changed, history isn't the same moving forward. Those ripples should distort the future and there won't be a separate Trunks to actually arrive at those points in time to prevent it from being overwritten.

If anything changed between the time after Freeza is defeated and the androids appear, I believe it was caused by Trunks, not Cell, and it caused by causality, not ripple effects.

When Trunks arrives in the past, he prevents Freeza's goons from spreading out and causing destruction, for example.

We don't know how it played out in the original timeline, only that eventually Goku teleported and took care of Freeza. We don't know if they caused destruction in the original timeline, or if Freeza and Cold themselves managed to cause some destruction fighting Goku since, despite being as strong as Trunks, Goku doesn't tend to be as quick as Trunks in finishing off the opponent.

It's perfectly possible, even probable, that those goons, for example, without Trunks' interference, were able to cause some destruction, and, as a butterfly effect, that would cause some difference in the future as a causality. Let's imagine that one of those goons spreads out and destroys a village killing everyone. In that village was a man that had a radio talk show and in the original timeline he never does anything else because he dies right then and there. But, in the timeline altered by Trunks, he goes on doing his job, and thanks to one of his programs that he didn't get to do in the original timeline, inadvertently, Gero, who had his radio on, has an idea, an epiphany for something he was working on and that would allow him to transport his brain into an android body and become an android himself.

Something as simple as that, caused by Trunks, can explain why it's #20 and #19 the ones attacking the city and not #18 and #17. And it explains it by causality, not by some kind of abstract ripple effects.

And, if it can be explained by causality, even if we don't know for sure what the causality was, I see no need to assume that there are some sort of ripple effects that change things randomly when one time travels. It seems to me far more logical to assume that it's causality, since it's perfectly possible for it to be because of causality.

As for other changes:

- Goku's decease striking later can also be attributed to Trunks, since his warning and all the training that Goku did thanks to it changed Goku's actions, and so that can easily explain the different timing for the decease; and

- #17 and #18 being stronger can easily be explained by the future androids not using their full power, as explained by future #17 before he kills Gohan.

There are no other changes between the defeat of Freeza and the androids appearing. As you can see, all can be explained by causality. There's no change that has to be attributed to Cell before he starts eating people.

In terms of Timelines, this means that Timeline 3, in my theories, in terms of events between the defeat of Freeza and the appearance of the androids, is exactly the same as Timeline 2, the only difference is that Cell is buried somewhere waiting.

[dbgtFO]

Instead of saying timeline creation are results of paradoxes, they are just created because you can't insert yourself in a time, that has already happened.

I think that's basically the same thing as paradoxes. Paradoxes happen because the time that the time traveler tries to enter has already happened relative to him. In other words, the chain of events going from the point that he is trying to enter will lead eventually to him and by entering it he is changing what would lead to him.

The thing where we seem to disagree is on the "relative" part. To me, even if something is on Age 9000, that can be the past of someone that is on age 8000 because he time traveled. Time is relative in that way.

Yeah, it's kinda the same, but I think how I see it, may be called something else. In any case, I just think, that as Trunks effectively travels to the past of the original timeline, he creates another one, that eventually becomes his happy ending timeline.

Anyway, guys, which one of the theories you prefer?

I prefer to take as much from the original story as possible and since we've deemed it possible, that Cell could come from a time, where Trunks beat Freeza and Cold, then I prefer number 2.

In the series, Cell traveling back and doing pretty much nothing but redevelop into his imperfect state causes Trunks to wonder how history changed so much.

Yes, but that's because Trunks is just a character in the story and though people may think what characters wonder about should automatically be true in-universe, I think it's a good idea to maintain a critical stance.

Trunks was a little baby, when the androids attacked. All the knowledge he has is going to come from second-hand information, so all his doubt can easily attributed to him not being around to witness what actually transpired.
The same with God and his speculation, that the androids are inherently nicer in the main timeline, because whatever.
His grounds for reaching that conclusion are utterly lacking and should not be taken as proof of anything, when he, himself, was not around to see what actually transpired in the original timeline.
He could not see an eventual developing of hatred towards earthlings during those ~20 years of unchallenged rampage, so drawing a conclusion based on the fresh androids not immediately being evil is faulty.
As Rereboy points out casuality explains everything, it just requires a little creativity.

[rereboy]

Yeah, it's kinda the same, but I think how I see it, may be called something else. In any case, I just think, that as Trunks effectively travels to the past of the original timeline, he creates another one, that eventually becomes his happy ending timeline.

Ok, so let's imagine he creates a timeline there.

Would that Trunks then go back to the second timeline, overwriting the duplicate? Or the third timeline?

And once trunks from Timeline 3 goes back home after Cell is defeated, wouldn't he go back to timeline 1, not timeline 4?

I prefer to take as much from the original story as possible and since we've deemed it possible, that Cell could come from a time, where Trunks beat Freeza and Cold, then I prefer number 2.

Awesome. I'm tending to that one too . I'm glad to have, after all this time, come up with something that is probably even better.

Also, I might later on put up a summary of events in timeline 2 that I think make sense and could easily have happened and that demonstrate how timeline 2 became very similar in the future to timeline 1

[dbgtFO]

Yeah, it's kinda the same, but I think how I see it, may be called something else. In any case, I just think, that as Trunks effectively travels to the past of the original timeline, he creates another one, that eventually becomes his happy ending timeline.

Ok, so let's imagine he creates a timeline there.

Would that Trunks then go back to the second timeline, overwriting the duplicate? Or the third timeline?

And once trunks from Timeline 3 goes back home after Cell is defeated, wouldn't he go back to timeline 1, not timeline 4?

No, Duplicate-Future Trunks(D-FT) just goes back and forth between the third timeline and the fourth timeline. He doesn't go to the original timeline as after creating the fourth timeline, he's now automatically linked to that and the third timeline. D-FT broke his link to the original timeline by trying to go a point in time, that had already happened.

[rereboy]

Yeah, it's kinda the same, but I think how I see it, may be called something else. In any case, I just think, that as Trunks effectively travels to the past of the original timeline, he creates another one, that eventually becomes his happy ending timeline.

Ok, so let's imagine he creates a timeline there.

Would that Trunks then go back to the second timeline, overwriting the duplicate? Or the third timeline?

And once trunks from Timeline 3 goes back home after Cell is defeated, wouldn't he go back to timeline 1, not timeline 4?

No, Duplicate-Future Trunks(D-FT) just goes back and forth between the third timeline and the fourth timeline. He doesn't go to the original timeline as after creating the fourth timeline, he's now automatically linked to that and the third timeline. D-FT broke his link to the original timeline by trying to go a point in time, that had already happened.

But if the machine is a duplicate of the original machine, wouldn't it have coordinates to the original timeline 1?

I get what you are saying. Basically, you envision that, however the way the machine works, the duplicate has now recognized timeline 4 as the original timeline (mistakenly) instead of Timeline 1. So, it goes back to it.

I think your conception works. It really just depends on how we figure the machine works

[dbgtFO]

But if the machine is a duplicate of the original machine, wouldn't it have coordinates to the original timeline 1?

I get what you are saying. Basically, you envision that, however the way the machine works, the duplicate has now recognized timeline 4 as the original timeline (mistakenly) instead of Timeline 1. So, it goes back to it.

I think your conception works. It really just depends on how we figure the machine works

Yes, probably the only logical problem with how I see it, lies here. I'm going to go in to a very deep rabbit hole, if I really try to come up with something, so I'm just gonna refrain from doing that and leave it at it really just depending on how we think the time machine works.

[Victorious]

So Rereboy, basically you think duplicate Future Trunks who killed Freeza in timeline 3, and the original Future Trunks in Cell's timeline /timeline 2 who killed Freeza "merge into one being" when heading back to timeline 1? Yet they split again when they go back to timeline 2 and 3? Hmm not sure if i buy that. What if some random person from timeline 3 like Goku or Roshi took Dupi's Time Machine and punched in the exact same coordinates? Would there be Roshi from timeline 3 and Trunks in the same timeline 1? Or would only Roshi be there? To me once the split is made they are seperate entities forever just like if Roshi took the pod, there would be two Roshi's in timeline 1. Another thing is Cell does change events in the main timeline, before he shows up in Ginger town. His travel must have caused changes to the main timeline that differ from his own even if his timeline was visited by a Future Trunks who killed Freeza. For one thing in Cell's timeline there is no evidence of #19 existing, and also he has no data on #16 so #16 doesnt exist either IMO. Their presence in the main timeline all must be explained by Cell's time travel IMO. Even if the first 4 years in the main timeline he lived what seems to be a passive existence just eating and digging in the forest he still caused it. IMO this why Trunks was constantly shocked at all the radical changes that were happening in the main timeline. So that means when Trunks is travelling back from timeline 1 to timelines 2 and 3, he is travelling back to timelines that are already distinct from one another.

[rereboy]

So Rereboy, basically you think duplicate Future Trunks who killed Freeza in timeline 3, and the original Future Trunks in Cell's timeline /timeline 2 who killed Freeza "merge into one being" when heading back to timeline 1?

No, that's just how I put the lines on the chart.

Both Trunks arrive at the same exact time and exact location on Timeline 1.

However, since it's impossible for them to occupy the same space at the same time (physical law) they would either both basically die, or one you remain while the other is basically "erased".

Think of a teleporter that tries to teleport inside a giant slab of rock. What would happen once he teleports? He is teleporting himself into solid rock. He can't physically coexist with the rock where he teleports to. So, his body would either become mixed with the rock and he would die, or the rock that occupies the space to where he is teleporting to would be erased by his teleporting.

We basically have the same problem with Trunks. There are two Trunks basically teleporting themselves into the same location at the same time.

So... what happens?

Imo, they either both die, or one basically erases the other, like a teleporter erasing the stone that occupied the place where his body has teleported to. So, one Trunks remains while the other is "erased".

Yet they split again when they go back to timeline 2 and 3? Hmm not sure if i buy that.

There is no splitting because there's no merging. The Trunks that remains and that has overwritten/erased the other, does exactly the same thing that the other would do because they are exactly the same in terms of knowledge, body and mind, and thus he travels to Timeline 2, following the same path.

The Trunks that appears later in Timeline 3 is a duplicate that was created when the timeline 3 was created. Timeline 3 is a duplicate of Timeline 2 and timeline 2 has Trunks arriving at two times in the future. Those events, just like every other past and future event from the timeline are copied to Timeline 3, and the only changes are the ones created by Cell (compared to timeline 2).

What if some random person from timeline 3 like Goku or Roshi took Dupi's Time Machine and punched in the exact same coordinates?

If they took Trunks' timemachine? They would go to timeline 1. Depending on the exact time that they went they would either create a paradox that would create yet another timeline, or not.

Would there be Roshi from timeline 3 and Trunks in the same timeline 1?

If they arrived at the same time as Trunks, once again, we would have the problem of them occupying the same space. One would be erased.

Or would only Roshi be there? To me once the split is made they are seperate entities forever just like if Roshi took the pod, there would be two Roshi's in timeline 1.

They do. But if they travel to exact same time and location... That's another issue, as I've explained.

Another thing is Cell does change events in the main timeline, before he shows up in Ginger town. His travel must have caused changes to the main timeline that differ from his own even if his timeline was visited by a Future Trunks who killed Freeza. For one thing in Cell's timeline there is no evidence of #19 existing, and also he has no data on #16 so #16 doesnt exist either IMO.

I've responded to that in my reply to TheDevilsCorpse. As you can see in that reply, I don't think that there's any change that can't be attributed to Trunks by causality.

Also, neither #17 or #18 had information on #16, and he still existed, so Cell not having information on him doesn't really mean anything. Especially since #16 is not relevant for Cell's objectives or interests at all.

Their presence in the main timeline all must be explained by Cell's time travel IMO. Even if the first 4 years in the main timeline he lived what seems to be a passive existence just eating and digging in the forest he still caused it. IMO this why Trunks was constantly shocked at all the radical changes that were happening in the main timeline. So that means when Trunks is travelling back from timeline 1 to timelines 2 and 3, he is travelling back to timelines that are already distinct from one another.

As I've explained in my reply to TheDevilsCorpse, there's no change that can't be attributed to Trunks. I've listed them in my reply and stated why.

[Victorious]

No, that's just how I put the lines on the chart.

Both Trunks arrive at the same exact time and exact location on Timeline 1.

However, since it's impossible for them to occupy the same space at the same time (physical law) they would either both basically die, or one you remain while the other is basically "erased".

Think of a teleporter that tries to teleport inside a giant slab of rock. What would happen once he teleports? He is teleporting himself into solid rock. He can't physically coexist with the rock where he teleports to. So, his body would either become mixed with the rock and he would die, or the rock that occupies the space to where he is teleporting to would be erased by his teleporting.

We basically have the same problem with Trunks. There are two Trunks basically teleporting themselves into the same location at the same time.

So... what happens?

Imo, they either both die, or one basically erases the other, like a teleporter erasing the stone that occupied the place where his body has teleported to. So, one Trunks remains while the other is "erased".

So if one dies or one erases the other, how do they go both go back. Dupi Trunks goes back to the main timeline for sure, and according to you [I don't necessarily believe this] the original Trunks goes back to Cell's timeline and dies there in a great battle with the Androids. Right?

I've responded to that in my reply to TheDevilsCorpse. As you can see in that reply, I don't think that there's any change that can't be attributed to Trunks by causality.

Also, neither #17 or #18 had information on #16, and he still existed, so Cell not having information on him doesn't really mean anything. Especially since #16 is not relevant for Cell's objectives or interests at all.

That's a good argument I guess, about #16, don't see anything real wrong with it for now. So you think in Cell's timeline though that #19 and robot Gero show up 9 miles south of South city like they did in the main timeline. Because you'd have to believe that too. I'm not sure I buy that.

]- #17 and #18 being stronger can easily be explained by the future androids not using their full power, as explained by future #17 before he kills Gohan.

Well I definitely cannot agree with this. #17 and #18 are definitely much weaker in the Trunks timeline [timeline #1 by your model] than they are in the main timeline. But they appear to be stronger in Cell's timeline as well. Since Cell in Ginger town knows Kamiccolo can match them. While Kamiccolo would stomp Future Androids #17 and #18 IMO. So IMO when Trunks came back and killed Freeza and prevented Goku from dying, this the cause of whey they are stronger, Goku likely lives longer and perhaps Gero is aware of this and made #17 and #18 stronger. So I don't think you need to worry about that for this current model, that's explainable. What's hard to explain is the difference between Cell's timeline and the main timeline. I feel they should be caused by CELL travelling to the main timeline, that didn't happen in his own timeline. In Cell's timeline there was no Cell from the Future.

[rereboy]

So if one dies or one erases the other, how do they go both go back. Dupi Trunks goes back to the main timeline for sure, and according to you [I don't necessarily believe this] the original Trunks goes back to Cell's timeline and dies there in a great battle with the Androids. Right?

I don't think you really understood how I made things work in my theories. The questions that you are asking don't really make sense unless you didn't understand my theories. Maybe if you explain your doubts a little better I'll be able to answer them better.

Meanwhile, I'll try to answer in few words:

They don't go both back. After the other was erased, there is only one that follows the same path. That means that he will go to Timeline 2, while in Timeline 3 there is a duplicate that didn't come from anywhere, he is just there because he is a copy of an event from Timeline 2.

That's a good argument I guess, about #16, don't see anything real wrong with it for now. So you think in Cell's timeline though that #19 and robot Gero show up 9 miles south of South city like they did in the main timeline. Because you'd have to believe that too. I'm not sure I buy that.

I find it much more likely than it being a random effect of time traveling or an indication of a more complex timeline theory. Those differences can be explained by causation, like the example I gave of the radio host surviving or not. A little thing like that being enough to change things, without anyone realizing the impact, to me, makes more sense.

]
Well I definitely cannot agree with this. #17 and #18 are definitely much weaker in the Trunks timeline [timeline #1 by your model] than they are in the main timeline. But they appear to be stronger in Cell's timeline as well. Since Cell in Ginger town knows Kamiccolo can match them. While Kamiccolo would stomp Future Androids #17 and #18 IMO. So IMO when Trunks came back and killed Freeza and prevented Goku from dying, this the cause of whey they are stronger, Goku likely lives longer and perhaps Gero is aware of this and made #17 and #18 stronger. So I don't think you need to worry about that for this current model, that's explainable. What's hard to explain is the difference between Cell's timeline and the main timeline. I feel they should be caused by CELL travelling to the main timeline, that didn't happen in his own timeline. In Cell's timeline there was no Cell from the Future.

Future #17, in the manga, as he is about to kill Future Gohan, states: "I didn't even use half my power last time."

Not only is Future Gohan absolutely chocked by this, which means that he wasn't aware, Trunks also wasn't there to hear it.

This means that the Future androids had been holding back for a long time now. Presumably, knowing them, to make the fights more fun.

And if they did it for Future Gohan, they probably also did the same for Trunks after that.

The logical conclusion is that Trunks, just like Future Gohan, is not aware that they are holding back, and thus, when he sees them not really holding back in the present, he is as shocked as Future Gohan was when he heard #17 say that he hadn't even used half of his power.

There is no need to try to justify the variation for their power with timeline theory when the manga itself already offers us a logical explanation for why Trunks said that they seemed stronger, and the manga does it with that single statement by Future #17.

After all, Trunks isn't all-knowing, it's only natural for him to not understand why they seem stronger if they had been holding back. He can't even sense their power level because they are androids.

And the variation in their attitude can also be explained by how long they had been allowed to roam free on Earth. Almost 20 years of being able to do what they want with no consequences just made them even colder. So, once again, causation explains it.

[Victorious]

I don't think you really understood how I made things work in my theories. The questions that you are asking don't really make sense unless you didn't understand my theories. Maybe if you explain your doubts a little better I'll be able to answer them better.

Meanwhile, I'll try to answer in few words:

They don't go both back. After the other was erased, there is only one that follows the same path. That means that he will go to Timeline 2, while in Timeline 3 there is a duplicate that didn't come from anywhere, he is just there because he is a copy of an event from Timeline 2.

According to your model, the Future Trunks we see in the manga to kill Freeza in the main timeline is the duplicate. That Trunks we know after killing Freeza 'left' timeline 3. He then game back to timeline 3 three years later in the Android saga, and finally returned back home to timeline 1 after the Cell Games. So that duplicate has two back trips to timeline 1.

Original Future Trunks
Leaves original Timeline for timeline 2 : kills Freeza
Returns home to timeline 1
Returns to Timeline 2/Cell timeline? Gets killed according to you.

Duplicate Trunks
Appears out of nowhere in timeline 3 as a duplicate : kills Freeza
Returns to timeline 1 for 3 years
Goes back to timeline 3 for the Cell arc
Returns to timeline 1 kills Future Androids and Future Cell.

So at what point was one of them erased? Because I don't get it. One needs to die in the Android battle in timeline 2/Cell's timeline according to you, while the other as we know eventually makes it back to timeline 1 and kills the Future Androids and Future Cell.

Future #17, in the manga, as he is about to kill Future Gohan, states: "I didn't even use half my power last time."

Not only is Future Gohan absolutely chocked by this, which means that he wasn't aware, Trunks also wasn't there to hear it.

This means that the Future androids had been holding back for a long time now. Presumably, knowing them, to make the fights more fun.

And if they did it for Future Gohan, they probably also did the same for Trunks after that.

The logical conclusion is that Trunks, just like Future Gohan, is not aware that they are holding back, and thus, when he sees them not really holding back in the present, he is as shocked as Future Gohan was when he heard #17 say that he hadn't even used half of his power.

Well that's a hypothesis but i'd just rather take Trunks word that they are much stronger. Either works. if you say they always hold back then they could have been holding back in the main timeline and so on. It definitely seems Future Trunks fought them on multiple occassions. In DBZ there's a million times we get fighters that suppress themselves, that doesnt mean later statements about their powers nessarily has to be about suppressed states.

[Desassina]

Can I post a revised scheme from the last time I did it here? I'll leave it as a spoiler:

Spoiler:

It's one universe with one timeline that has evolved through many instances until it stopped with Gohan's victory. The 3 models (top, middle, bottom) have these steps with a different display, but they're ultimately the same with a superposition, until we can only see two of them.

[rereboy]

He then game back to timeline 3 three years later in the Android saga,

No. The Trunks that appears later in Timeline 3 is not the duplicate that traveled earlier from Timeline 3.

The duplicate that traveled earlier from Timeline 3, went to Timeline 1, overwrote the other Trunks, and then went to Timeline 2, following the same steps that the overwritten Trunks would have taken.

The Trunks that appears later in Timeline 3, like I said, is a copy, a duplicate that was replicated when Timeline 3 was born. There's no Trunks traveling to that point in time in that timeline. That Trunks is there because he is a copy of an event, just like the earlier Trunks that killed Freeza appeared in the Timeline (3) simply because he was a copy.

Well that's a hypothesis but i'd just rather take Trunks word that they are much stronger. Either works. if you say they always hold back then they could have been holding back in the main timeline and so on. It definitely seems Future Trunks fought them on multiple occassions. In DBZ there's a million times we get fighters that suppress themselves, that doesnt mean later statements about their powers nessarily has to be about suppressed states.

In the main timeline it doesn't make much sense for them to be holding back because no one comments on that, even when the androids are fighting people who are comparable to them or superior.

For example, when Piccolo, after fusing with Kami, fights the androids, he never says "hey, you were holding back before". Nor does he comment or implies that he surprised by their power. Which means, imo, that they (#17 at least) are within somewhat his expectations. And since the androids ended up being in danger against Piccolo, and then against Cell, it's clear that they weren't actually holding back.

It's therefore clear, imo, that the androids in the main timeline, weren't really holding back on their power. At least, certainly nothing like using just half their power like Future #17 mentions.

Trunks wasn't lying, he just didn't understand exactly what the issue was. He also didn't understand that Vegeta could have used grade 3 but had chosen not to, and instead he assumed that he had achieved something that his father hadn't. It's just a wrong assumption, it happens.

[Speedster]

For the time being I read only your first theory, so I will give you feedback only on that. The main issue for me is where the one of the Trunks’ doppelgängers returns. You basically suggest that the Trunks doppelgänger who dealt with timeline 2 and who had already returned to timeline 1 magically popped out of existence the moment Trunks who dealt with timeline 3 went back to timeline 1. Remember that the Trunks who dealt with timeline 2 had already returned to timeline 1 at a different time point and he was living his life there with Bulma. Unless you ignore time passage and assume that the two doppelgängers went back to timeline 1 simultaneously and somehow merged on arrival. You can argue that regardless of how much time the two doppelgangers spent in timeline 2 and 3 respectively, their time machine would get them back to say 18:33 of May 12 of Age 785.

But there are huge problems after that. How were the Androids of timeline 1 actually defeated after all? With the remote (as per the Trunks who returned from timeline 2) or by Trunks killing them (as per the Trunks who returned from timeline 3)? We have history of the actions in timeline 1 of the Trunks who dealt with timeline 2. Are these reverted when he gets overwritten in favour of the Trunks who dealt with timeline 3? If no, which Androids does the Trunks who dealt with timeline 3 gets to kill when he returns to timeline 1? There will be none! Or which Trunks does Cell of timeline 1 gets to kill to steal his time machine and get back in time? If after his return to the future there is only the history of Trunks who dealt with timeline 3 then he will kill Cell preventing him from going back in time. And then what happens with the Trunks' increase in strength which was a result of him having to face Cell in timeline 3?

As all this create a paradox you can well have a 4th timeline then, where Trunks from timeline 3 returns - a timeline without the effects of the actions of the returned Trunks who dealt with timeline 2. Which 4th timeline, in essence, can be thought as the timeline from where the Trunks who dealt with timeline 3 originates and returns. And timeline 1 is the one from which the Trunks who dealt with timeline 2 originates and returns. Which concept is identical to this video: https://www.youtube.com/watch?v=lh58fPJtfR4