Déjà vu

Déjà vu.  We've all experienced it, though some of you may not know it by that name, or even that it had a name.  It means 'already seen' in French, and  is the experience of feeling sure that one has already witnessed or experienced a current situation, even though the exact circumstances of the prior encounter are uncertain and were perhaps imagined.

Some say that a déjà vu is a glitch in the Matrix

I can haz teh invizibl glitchez?

Another explanation (and it's going to be far-fetched, but I don't see you coming up with anything, so sit down and shut up) is that Earth has always been populated with a certain group of time-travelers, ones whose mission has been to go back in time and try to change specific events in our history, such as the Lincoln assassination.

Of course, that still happened, so either they figured out it would behoove them not to do it, or we were left in this dimension, and the time travelers created a new timeline.  Something like that.  Anyone with a cursory knowledge of theoretical time travel knows that going into the past is impossible, due to the whole feedback thing. 

You know how when you put a microphone up to a speaker, the sound and interference builds and builds until the speaker explodes?  Well it's the same with wormholes.  The radiation getting transferred to the past as the time traveler goes through joins the same radiation in the past, which stays around until it gets to the present, where it doubles and builds up, and much like the music speaker, the wormhole can't handle it, so it explodes or implodes.  Either way, it ceases to be.  And word on the street is that the radiation builds up so quickly the time passage expires almost before it was created.

But lets say time travel to the past were possible and there were time travelers going back and changing specific events.  Each time they go back, they're creating another layer, or dimension, on top of all the pre-existing timelines.  And each time they do, the layers of alternate timelines get thinner and thinner.  Of course, since they try to maintain things as unchanged as possible (except, of course, what they went back to change), not much will change in your life.  You will probably do mostly the same things in your life in the alternate timeline as in the original one.  For example, you may go to the bathroom at 12:30 in one dimension, but at 12 in another.  When you and the alternate you cross offset paths like that, you sense it.  Deja vu.  That's the hypothesis, anyway. 

Here's an article on how deja vu works from a more scientific angle