While watching Harry Potter and the Prisoner of Azkaban, I've had an idea. If you were hit with a rock from a person you didn't see as a result of time travel, then doesn't that mean that there's no universe in which that thing didn't happen because it always happened as a result of you time travelling therefore there's no beginning to the cycle and no end? Because when you get hit and reach the future where you went back in time you would go back in time and do it again. So my theory is that travelling in time has no beginning and the future is laid out in front of you and cannot be changed.
Please don't get his hopes up His peers are bound to think it's a great idea/insight Please Register or Log in to view the hidden image!
Not to burst your bubble, but this is not exactly a novel idea. It is simply the " predestination" solution to the 'Grandfather paradox'. (You can't go back and kill your grandfather before your father was born and thus prevent your own birth, because whatever you do in the past actually leads up to your being born.) This of course leads to the complete loss of free will, as all events are predestined. This is how time is treated in that particular movie. However, that was for the purpose of plot device, and should not be taken as a serious model for time. Once the author used this in the movie, they forgot about it and never used it again plotting out any of the rest of the movies. In general, it is not a good idea to model your ideas on time based on plots in fiction. The writers of such fiction almost never really work out the full consequences of their usage of time travel, and merely mold it to fit the needs of the story they wish to tell. The simplest solution to time travel paradoxes to to merely assume that travel to the "past" is simply not possible in the first place.
The next best thing is to just assume that travelling to a past point splits it into an alternate timeline.