No Time Paradox?

[T38]

We all know that Future Trunks went back in time to save Goku from a heart virus. And we all know that he stayed for a while to fight alongside the Z warriors in the Cell saga. But the story writer seems to have made a huge mistake in this saga of DBZ - there is suppose to be a time paradox somewhere in between. If Androids 17 and 18 became good guys after Cell's death in the current time line, why are they still bad guys in Future Trunks' time line? I guess the story writers didn't know what time paradox was when they created DBZ.  

[Nandesca]

The time travel theory they used in DBZ was the fracture effect. Basically when you go back in time you cause the time line to fracture into two different time lines. One being the original the second being an offshoot. It is imposable to change time in your own timeline. If it happened then what you changed would not happen thus you would not go back in time to change what happened from happening. The fracture theory is believed to be the means in which the universe keeps a paradox from happening.

Source from Wikipedia.

The possibility of paradoxes
The Novikov self-consistency principle and recent calculations by Kip S. Thorne[citation needed] indicate that simple masses passing through time travel wormholes could never engender paradoxes—there are no initial conditions that lead to paradox once time travel is introduced. If his results can be generalized, they would suggest, curiously, that none of the supposed paradoxes formulated in time travel stories can actually be formulated at a precise physical level: that is, that any situation you can set up in a time travel story turns out to permit many consistent solutions. The circumstances might, however, turn out to be almost unbelievably strange.[citation needed]

Parallel universes might provide a way out of paradoxes. Everett's many-worlds interpretation of quantum mechanics suggests that all possible quantum events can occur in mutually exclusive histories.[44] These alternate, or parallel, histories would form a branching tree symbolizing all possible outcomes of any interaction. If all possibilities exist, any paradoxes could be explained by having the paradoxical events happening in a different universe. This concept is most often used in science-fiction, but some physicists such as David Deutsch have suggested that if time travel is possible and the many-worlds interpretation is correct, then a time traveler should indeed end up in a different history than the one he started from.[1] On the other hand, Stephen Hawking has argued that even if the many-worlds interpretation is correct, we should expect each time traveler to experience a single self-consistent timeline, so that time travelers remain within their own world rather than traveling to a different one.[11]

Daniel Greenberger and Karl Svozil proposed that quantum theory gives a model for time travel without paradoxes.[45][46] In quantum theory observation causes possible states to 'collapse' into one measured state; hence, the past observed from the present is deterministic (it has only one possible state), but the present observed from the past has many possible states until our actions cause it to collapse into one state. Our actions will then be seen to have been inevitable.  

[reven228]

but what about android 13. he appeared in that one to. it probably was to popular demand but the writers should have improved on the reason that trunks appeared. i mean he was able to beat cell, and cell was able to beat goku, and in the movie goku beats android 13. it's just a huge headache, give me some info plz.  

[Nandesca]

reven228

but what about android 13. he appeared in that one to. it probably was to popular demand but the writers should have improved on the reason that trunks appeared. i mean he was able to beat cell, and cell was able to beat goku, and in the movie goku beats android 13. it's just a huge headache, give me some info plz.

The DBZ movies are never cannon. Its best to not dwell on the things that happen in them when they are compared to the series.  

[lachampck42]

Im new here thank u for the info!And u put it that way then that doesnt make sense.  

[jdkornuta]

Another thing is how cell is still alive in the future?  

[darkzumi]

Time travel NEVER makes sense! razz Dragon Ball Z uses the "fracture" theory Nan described above. It is the least headache-inducing one to use. biggrin