The rules of fictional time travel never work. Unless the plot is highly constrained adding time travel to the mix will generate self-multiplying plot holes through which the audience can fall and end up trapped in an unending loop of ‘but why didn’t they just…’
In attempt to resolve all time travel plots ever, let me suggest the meta-consistent theory of time travel. The theory does not offer a consistent model of time travel but rather a theory that makes all inconsistencies consistent with a more abstract level of consistency.
Here is how it works:
- Time travel has the capacity to change the past.
- Time travel that just goes into the future without any capacity to return doesn’t generate any inconsistencies anyway (it is the equivalent of going to sleep and waking up several hours in the future).
- If you travel into the past then something is in the past (you) that wasn’t there before or there in that quantity (e.g. a past you and a future you).
- Time travel requires super-duper amazing physics.
- Time travel to the past can’t be easy because otherwise everybody would be doing it.
- Time travel changes the physics of the past.
- This isn’t demonstrable but it makes the theory fun and so I’m asserting it on aesthetic grounds.
- So each journey into the past change the nature of physics somewhat.
- Because of 3 we can therefore assume that each time travel journey works in a different way each time.
- Your first trip in a time machine involves super-duper physics version 1
- Your second trip in a time machine (assuming it still works) involves super-duper physics version 2
- ..and so on
- So time travel should therefore be presented inconsistently. Time travel to the past should operate, at some level, differently each time.