Another time travel theory!

[Xyex]

First, hello again everyone. Though... I'm not sure who's all still here from 'the old days' now.

Anyway, on to the thread. I was recently working on some time travel stuff for a fanfic and was looking back at some of the old time travel theories we developed on this board. As I was trying to plot stuff out and integrate my new timelines into the pre-existent mess created by Trunks and Cell I suddenly realized that the mess perhaps wasn't as messy as it first seems. A little more work, and I'd developed this new idea I call the "alien traveler theory." Here's how it goes:

Timeline One - Original Timeline - This is the first timeline we see, where Goku dies of the heart virus and the Androids appear. Trunks eventually travels into the past to warn of the Androids, then returns home. Time passes and he goes back a second time to help against them, then returns home again to deal with the Androids of his own time. Between this return and his next planned trip back some alien on some other world also travels through time. Then Trunks goes to make his last trip but Cell intervenes and steals the time machine, going back in his place.

Timeline Two - Unseen Timeline - This is the timeline that the Trunks from TL1 created when he went back to warn of the Androids. It is also the timeline he returns to on his second trip back. Future Cell does not appear here and we never see this history in the series.

Timeline Three - Alien Traveler Timeline - This is the timeline created by the alien time traveler from TL1. His destination was pre-Trunks arrival, so he entered into TL1 splitting this history off from that. As a result the events on Earth unfold the same as in TL1 with this Trunks also traveling into the past. This is the timeline where Trunks defeats Cell.

Timeline Four - Cell's Timeline - This timeline is created by the Cell from TL1 when he stole the timemachine and traveled into the past. It splits from TL3. Future Trunks does not appear in this timeline.

Timeline Five - Series Timeline - The Trunks from TL3 goes back to warn of the Androids and enters Cell's TL4 causing this timeline to split from that one. Thus TL1 Cell also exists here. This is the timeline we see in the series.

[FoolsGil]

Can you like do a graph or something? I don't even understand why the alien is there and I read this five times. I can understand the timeline splitting because of the alien. But why does the alien interference creates a timeline where Trunks defeats Cell?

[Xyex]

The alien is there only to explain how we have a timeline in which both Future Trunks and Future Cell are present in the past. His entire purpose is simply to create a second timeline that is exactly the same as the original one (at least on Earth). And it's not the alien that allows Trunks to defeat Cell, not exactly. The alien simply enables Future Trunks to be present in a past that also has Future Cell, thus allowing him to become strong enough to defeat Cell upon returning home.

[Speedster]

Your theory is a bit flawed as there would be more timeline branches created if a third time-traveller existed. When a new timeline is created by a time-traveller the rest of the time-travellers are destined to act the same in any timeline (unless something is changed) so they are destined to travel back in time from some of those alternate timelines as well creating even more parallel timelines.

For example Trunks travelled back in time both from the original one (where with the blueprints he defeated the Androids with the remote) AND the “History of Trunks” (where he defeated the Androids and Imperfect Cell by being strong enough). That was because Trunks was destined to travel back in time if the events of the timeline played similarly to those that made him to go back in back in time in the first place. Cell was also destined to travel back in time if he couldn't find the Androids in his present timeline. And had he not been killed in the "history of Trunks" timeline he would have travelled back in time creating yet ANOTHER timeline.

As you can see a 3rd independent time-traveller would complicate matters a lot. Time travel in canon Dragonball is simple only because it involved 2 travellers, one machine and only two timesplits due to how the events played out. By the way the third time-traveller might as well be Tapion from movie 13 when he travelled 1000 (or so) years to the past.

[Xyex]

While it's true that the alien traveler would end up repeating their trip in the Unseen Past, that's the only extra trip that would happen. All the other timelines already include the alien traveler's changes, That one extra trip doesn't influence the timlines in question, so it doesn't really complicate anything.