I think that if ANYBODY had a GOOD grasp on this concept, we would already be making history....or changing it?

the speed of light is relative to the observer. if an observer is going half the speed of light and someone (who was standing still) shone a light in the same direction as the observer is going, the observer would see the light zoom past him as if he had been standing still. (or the speed of light + speed of observer.) for this to be possible, something has to change to keep the speed of light the same. this is time. as you get closer to the speed of light time has to move slower around you in order for the speeed of light to be relative. because of this, you would go forward in time faster than normal. say you and you friend are standing next to each other, you decide to get into a rocket ship and fly off at the speed of light. you're gone for ten years. when you get back to earth, you're friend is 10 years older, but, because you were travelling at light speed, time moved slower around you therefore, for you, it only felt like five years. i hope this helps and i hope this is acurate! lol

THEORETICALLY if you traveled faster than light you would go back in time. Realisticly the faster you travel the slower your own time progresses and you basically are going into the future. That's because space & time are the same thing, a 4 dimensional spacetime where the faster you travel the slower you age. That's all I know.

Unfortunately, I am not a physicist nor do I play one on TV. However, Einsteins theories on relativity, do indicate that this is the way to move in the direction of time travel. He proved that the faster an object moves, the slower time acts on that object (although this has never even been close to replicating the effects that the speed of light could have on an object). Granted this is a very elementary explanation of this phenomenon. You can get more info here: http://en.wikipedia.org/wiki/Time_travel

I can't answer this question in full, however, what I can give you... We can not travel faster than the speed of light if we initially start below it (e.g. at no point can you hit v=c). This does NOT in any way forbid faster than light travel, but it just means the particle has to exist naturally at v>c. A theorised particle is the 'Tachyon', that travels faster than the speed of light. I don't know overly much about it, but I'm under the impression that it would essentially 'appear' to travel backwards, however if we could create a Tachyon source, we would know it is the emitter and the other bits are the detectors, and thus we would KNOW it has been travelling "back in time" as such. I can't really comment on what time scales we can possibly go over, and if it is actually "time travel", a mathematical construct, or just a localised effect (e.g. in various rest frames, but overall this general concept of space-time is conserved, e.g. if it travels for an infinite amount of time it won't end up at the big bang). That's beyond my current scope and, as far as i know, 'serious' physics at the moment (like i said, mainly theoretical).

Relativity: One man's space is another man's time -- if there is any relative motion between those two men. A "reference frame" is a state of motion, straight line, constant velocity. Two observers are in different reference frames if there is any relative motion between them. An "event" is a point in spacetime. Two events are related "timelike" (if one is inside the other's light-cone), "lightlike" (if one is on the other's light-cone) or "spacelike" (if one is outside the other's light cone). All of the above is general enough to be either Newtonian or relativistic; what follows is relativistic. When two events (say A and B) are related in a "spacelike" way, there is some "reference frame" in which A precedes B, and there is another reference frame in which B precedes A. So there is a way for an observer to move (in a straight line at constant velocity) so that the observer would observe event A preceding event B; and there is another way, vice versa. If it were possible to travel faster than c, then it would be a "spacelike" path (not a timelike path or a lightlike path). So in some frames, you'd be going backward in time. Also, with spacelike paths, you could go somewhere and come back, in such a way that you arrive before you began (i.e. your final arrival event would be in a timelike relationship with your starting event). (I almost said "come back to the same place" but there is no such thing. "Same place" is in the eye of the observer and varies with reference frame.)