How does Trunks' timeline even exist?

[Doctor.]

The way the story is supposed to go is that Goku dies from the heart virus and the androids wreck the Earth. This is the original timeline, timeline 1.

In timeline 1:
- Bulma creates a time machine
- Trunks goes back, comes back, goes back again, gets the blueprints of the androids and returns
- Androids are deactivated with a remote control
- Cell kills Trunks and steals his time machine

Basically timeline 1 is the original and Cell's timeline. When Trunks goes back to the past, he creates a new timeline, timeline 2.

In timeline 2:
- Trunks comes and slices Freeza, gives the antidote to Goku
- Returns 3 years later to help fight
- Androids are deactivated with the remote control
- Trunks returns to timeline 1

This is the unseen timeline, the one we know nothing about. We can assume that Cell never showed up because he set the time machine to an earlier time than Trunks did, causing another split and creating another timeline, timeline 3.

In timeline 3:
- Cell arrives
- Trunks arrives and gives Goku the antidote
- They defeat the androids and Cell

Pretty straightforward, it's the timeline we're following right now. Except we know there's a 4th timeline, the one Future Trunks 2.0 comes from. But how can this timeline exist? Until now the existence of all the other timelines makes perfect sense. 1 is the original, 2 is a product of Trunks coming back in time and 3 is a product of Cell coming back even further. So how can 4 exist? 4 is obviously not the future of 3 because in timeline 3, Cell should have killed everyone after Goku died of the heart virus. There's no way a second timeline like Trunks' could exist.

[Doctor.]

Shit, in Cell's timeline Trunks killed Mecha Freeza.

Ok, I'm lost.

[Cetra]

What happens with the Unknown Trunks?


One possibility, more follow down below:

- He starts on the Timeline of our Future Trunks and travels back in time
- He reaches a Time Branch where a) has not arrived before and b) with his own arrival the conditions No and Yes are met
=> A timeline that we have not seen is experienced by him
- He jumps back to his branch, not arriving on a single branch though but creating an two additional branches "on this branch" (so just another fork) as he already has fulfilled several conditions that another Future Trunks from the same timeline has not fulfilled, therefore arriving on that new time branch, he kills 17 and 18 and is killed by Cell

So basically Trunks starts on the timeline our Future Trunks knows but after they started their time travel they never returned back to their original timeline but a branch that came after their original timeline which rooted from their own different events.

The Mecha Freeza condition is a variable that is either a plothole or a condition that brings in too many possibilities to provide an actual answer because it means Trunks has arrived and Goku did not die. Therefore he warned them. Basically it is possible that they still died, leading to another Ruined Alternate Future which is Cell's Timeline (and in that case it would not be a branch of our Trunks' time instead of what I mentioned before). But that, as said, has too many unknown factors as, even though it is very possible that they still lost, at least Piccolo should have been able to kill them (if he did not die before or did not "not decide" to reunite, that is).

So basically there are some possibilities of how events could have turned out. Even without that one I would not call it "perfect sense" because that time tree stuff is always a very uncertain thing, full of problems and through the lack of guarantee that xyz happens basically very questionable to be possible in the first place.

One of the possible time trees for that question:



It is possible that this "Cell timeline" is either the result of the Future Trunks that we know (from the No-no-timeline) who just happened to travel to the No-yes-timeline, creating the Cell timeline this way and opening the path for the "Unknown Cell line Trunks" who then also did some time travelling where we do not know on which branch he arrived OR the Cell timeline is the result of a bootstrap paradox (Song of storms paradox) of the Cell timeline Trunks himself who arrived at the start of his own timeline, being the cause of this timeline and thus being a part of its inevitable doom. The very fact that multiple Trunks exist in multiple ruined timelines also makes it possible that the "Trunks?" question on my sketch can actually also get more complexity by being split up into more questions for more timelines - and as one can think, there are basically many more anyway. Also, if it is a bootstrap paradox then its existence is 100% guaranteed therefore would that reveal even more complexity of the time branch instead of that simple "No-yes". But for the sake of simplicity, let's leave it at that.

[Cipher]

Shit, in Cell's timeline Trunks killed Mecha Freeza.

Ok, I'm lost.

The only way time travel in the series doesn't become a massive mess if you write that line of Cell's dialogue off as the kind of error Toriyama occasionally adds writing week to week. If you ignore it, the whole system is amazingly consistent, if a little obtuse for fictional time travel.

Anyway, Trunks' timeline exists as a result of his experiences in a Cell-altered past. It would splinter the moment he first returns to his future, technically, but the big split obviously comes when he's able to defeat Cell.

I'm going to quote myself from another timeline thread currently active on this board breaking down the series' four timelines. It's a wall of text, so spoilering as to not stretch the page:

[spoiler]Trunks and Cell create three timelines (bringing the series' total to four). There are two lines in Cell's dialogue that clutter up the series' time travel model to absurd degrees, so I'll cover those below and why they're better thrown out. It's just the kind of thing that happens writing by the seat of your pants week to week.*

A) The original timeline, which exists without intervention from any other time travelers, is Cell's -- the one in which he kills Trunks and steals his time machine. Of course, by the time he emerges, Trunks has already gone back to the past once and found an undisclosed way to defeat the androids, which brings us to ...

B) The second timeline, which is the "unseen" timeline altered only by Trunks. We know nothing about what happens here, but it must exist for Trunks to have found a way to defeat the androids in the original timeline. Once Cell kills this Trunks and goes back a year before he originally arrived, he creates ...

C) The third timeline, which is the timeline of the main series, altered by both Cell and Trunks. This is the one we see play out. Trunks arrives to meet Goku, and several years later, when he returns to help fight the androids, everyone realizes time has been further altered by a second time-traveler, whose time machine is found by Bulma in the woods. This turns out to be Cell.

This timeline confirms a couple of things people don't always pick up on. The most important is that Trunks' time machine appears to enter the last-altered past. Or rather, when events are changed, they create a sort of de-facto "past" it enters. Cell winds up in a timeline destined to have Trunks arrive in it, because that's what the past looks like at the point he steals the time machine. From another perspective, the Trunks we come to know as ours enters a past that has already been altered by Cell.

Coincidentally, this is also why Trunks is able to move back and forth between the main timeline and his own, as long as he always arrives after his last departure. More on that below.

D) The fourth timeline, which is Trunks' divergent future, the result of his experiences with Cell in the past. Technically Trunks' future would split off the moment he leaves after giving Goku the heart medicine, based on whatever butterfly-effect changes might have occurred due to Cell's presence. But the big difference is that after the meat of the arc is done, Trunks is able to return to his own time and defeat both the androids and Cell. This is "our" Future Trunks, whose experiences with Cell in the past wind up creating an alternate future timeline than the one that first existed.

*The lines of Cell's dialogue we have to throw out involve a comment about Trunks defeating Freeza and Cold in his timeline (despite Future Trunks remembering Goku doing the deed, and there being no reasons for their timelines to have split at that point), and a line about the time machine already being set to arrive a year before Trunks' original debut. The former just clutters things up to an absurd degree, and the latter -- while there are in-universe explanations; perhaps Trunks wanted to create yet another timeline totally free of the androids -- is more trouble than it's worth. Especially because it ignores the very tidy explanation that Cell has a four-year maturation period. If that's the case, it makes enough sense that he'd intentionally arrive four years prior to the androids' activation, to be able to absorb them as soon as possible.[/spoiler]