"We have to go back!" "Back where?" "BACK, to the FUTURE!!"

Lately, I've been thinking about time travel. Not the most original of thoughts, but still something to mull over during the wee hours of the morning.

I cannot remember which show, [if you know which one, PLEASE let me know :)] but one had a very interesting theory which I shall share with you all now (with a little David-ness thrown in, of course).

Let's say you have an event on a linear time scale (because time is linear):
--------*Past*------------------Event---------------*Future*-----
The past is before the event, and the future is after this event.
Now, let's say the event has JUST happened, and you wish to go change it ("P" represents person)
--------*Past*------------------Event--*P*-------------*Future*-----

Now, if you wish to change the event, taken for granted that time travel is possible, you would go to your past (pre-event) to change it. Two "*" represent time travelled person, while ^T^ represent the person's original time
--------*Past*----------**P**--------Event--^T^-------------*Future*-----
Everyone with me so far?

Now, what is you tried to change it, but the event stayed the same? This is known as causality, which is "cause-and-effect". What if the effect occurs regardless of the cause?
For example, what if Lincoln was not assassinated in Ford's theatre? But was murdered outside the theatre by a different shooter? Lincoln would still be dead, so time 'course-corrected' itself.

BUT, now for the fun stuff. What if you SIGNIFICANTLY changed the time before the event? For example, you tried to prevent it, but instead caused a mu;lti-vehicular collision, which caused a public outcry, which resulted in total governmental control of the state/province? This creates what is known as an alternate timeline.
ooooooooooooooooooooooooo-----------------------------*Future*--------
-------*Past*----------**P**-/------Event--^T^-------------*Future*-----
The "/" represents the split in space-time, which caused an alternate reality that diverges from the normal timeline, while the "o" represent a time BEFORE this timeline was created. Both time line's still exist, just in separate dimensions.

If you're lost, this will help. Remember "Back to the Future Part 2"? In it, Marty attempts to buy a 2000 Sports Almanac from the future to capitalize on knowing the results of sport events before they happen in his real time line of 1985. However, it gets taken by future Biff, you steals the DeLorean and gives it to his younger self. Biff then uses this to become a multi-millionaire who murders Marty's father to marry Marty's mom. So, when Marty travels back to 1985 from the future, everything is different because of a separate timeline was formed by Biff becoming a millionaire. And the only way to resolve it? Went back in time, AGAIN, to steal the almanac before Biff can use it.

Fun stuff, eh? And THIS is what I think about when I'm BORED!!!!!

Catch y'all later!