The theory of time travel is that if you can get a metal object to go at the speed of life you can acheive time travel. He talks to his sceince teacher about this entire thing and then the sceince teacher gives him a book on time travel. The book describes everything he sees smells feels and everything. One example is how spear type things come out of peoples chest that show where he is going.
    Then Donnie gets into another discusion with the teacher. He talks about being able to see into the future through gods channel which allows him to choose his own destiny. Donnie starts contidicting what he is saying because he says that all life is pre decided, but if you look into gods channel you have a chance to change your destiny.