I've heard of one idea which argues that when you go into the past and kill yourself (assuming that such a thing is possible in the first place), you physically create two different histories of yourself, which basically means that in one universe you are alive while in another universe (or a multiverse) you are dead.
Then again, the whole time travel thing is just a little too complicated for me to understand.
Then again, the whole time travel thing is just a little too complicated for me to understand.