Many sci-fi movies, television media, and video games feature the Time Traveling concept. Someone goes back in time to fix something, and then goes back to the future to see it fixed. Many people wish it could be this easy, but behind that fun entertaining concept, is a mindfuck of horrible consequences. I'm gonna point out some major flaws with Time Travel, so we can discuss it in the topic.
1. Novikov self-consistency principle
This theory says that anything a time traveler does in the past must have been part of history all along, and the time traveler can never do anything to prevent the trip back in time from happening, since this would represent an inconsistency
Sorry Sonic 06, but I'm gonna have to use you as an example here. In Shadow's Story, when Mephiles is first released, he has the form of shadow, and ask him if he remembers him back when Shadow first sealed him up 10 years ago. Well, if that's true, then that means that Shadow already sealed him, and the adventure already happened, which is impossible because the adventure was permanently erased at the end of the game.
Almost everyone does this, with no logical explanation as to why the thing is there if they already time traveled, yet haven't time traveled. Many people will argue with the fact that when someone goes back in time, they permanently change the course of history and make it so that whatever they do then, will always happen in the future. Which is still confusing as fuck, but brings me to my next example.
2. Alternate Timelines/ Multiple universes
In DBZ, Krillin asks Trunks why can't he just go back in time, kill the androids, and then the future would be saved. Trunks says he can't do that, cause not only would this timeline be un-affected, it would create another timeline. Yep, it's the "Alternate Timelines" cliche.
Basically, say if my friend died, and I traveled back in time to save him. When I go back to the future though, he's still dead. Not only have I failed in saving him in this timeline, I have subsequently created another time line in the universe. So I fucked up right? Well for example, let's say if I didn't go back in time in the first place, I would have died, because there was a bomb about to go off or something.
So I want to go back in time, and tell my past self not to go back in time, because it would be a waste of time. I do it and convince myself not to go back in time, which unfortunately means he will be killed by the bomb. Now I have fucked up twice, by creating yet a 3rd timeline. I can either stop here, and let the three timelines be, or go back in time again, stop myself from going back in time again, and save myself from dying, which would create another timeline. And again, and again.
I'm sure many of you Zelda fans already know about this, lol.
3. The Butterfly Effect
A person who time travels to the past, can change history, whether intended or not. Since I'm a lazy bastard and have not that much knowledge with this effect, I'm gonna just copy-past an example from the Wikipedia page.
The most well-known example of this theory is the 1985 film Back to the Future, in which the protagonist Marty McFly goes back in time and interferes with his parents' first romantic encounter, thus erasing his own existence (as well as that of his siblings). However, the effect only happens gradually, exemplified by a family photo in his possession: each of his siblings begins to disappear limb by limb, starting with the oldest and working down to him (the youngest of the three). This allows Marty to correct the error and restore the timeline, albeit with a few minor changes that are due to his interference. This effect has one contradiction - If a person, somehow, causes himself to not be born in the past, then he would not have been able to do the thing that caused him to not be born for he would have not existed, thus causing time to corrupt.
Point taken, NEXT.
4.The Merging Timelines theory.
This is the opposite of the Alternate Timelines theory, where instead of creating multiple timelines, the person actually becomes apart of that timeline.
This is more common when traveling dimensions though, so I'm gonna make this quick. Basically, if someone where to meet a copy of himself from another time/dimension, the two copies would merge, thus making that person the same person from both of their origins. It's confusing as to see which one is from originally from which, or if both have been apart of the same timeline or something. I'm getting confused just from writing this!
5. It will always happen because it is Destiny!
Going back to my example in number 2, say if I did save my friend, and he was alive back in our timeline. Now say if he gets shot a week later, so I go back in time and save him again. Everything's fine and dandy, that is until he gets run over by an ice-cream truck. So I go back in time, and save him again, and well you can see where this is heading. Basically he was meant to die, yet I keep disrupting the timeline and saving him. So now Destiny/Fate is pissed at me, and is now trying to kill him at every turn, until he stays dead.
It's kinda like Final Destination, only with Time Travel involved.
6. Oh, I just fucked myself over didn't I?
This one goes back to the butterfly effect. Marty goes back in time, and tries to change the past. This works for the most part, until he starts to disappear because he fucked up history, making him not exist anymore. It's a common trope that many movies use, and if you wanna find out how to fix it, watch Back to The Future.
7. Go back in time, fix it, Everything is okay now!
The most common trope used in every single form of media, and ironically the most unrealistic one.
Man goes back in time to save his dead Wife, succeeds, everything is now a-okay! That's it, no plot twist, no "monkey's paw" thing, just you going back in time and succeeding in what you strived to do in the first place. This is the one most people believe will happen with time travel. Oh how I wish this could happen, but as we all know, Time Travel's a bitch, ain't it?
(Please, feel free to add more Time Travel theories I may have missed)
Edited by Mike Dawson, 13 November 2011 - 06:42 PM.