Time Travel - is it possible?
In order to grasp the possibility of time travel, you've got to understand what time actually is. Time is merely the movement of matter. That is to say the smallest unit of time, is the time it takes for the fastest moving piece of matter, to move the distance of the smallest piece of matter.
Now considering "time" is only the movement of these particles (time is the constant), how can you go back in time? or unmove all the universes particles?
The speed of the particles can not change, because that would mean the speed of light (a constant) must change, or the smallest unit of matter must change. Both of which are impossible.
Honestly... it's simply impossible to travel back of forward into time.
Even if we looked at the universe through the string theory, multiple identical dimension, bullshit idea of the universe. For something to physically move from this universe to another point in time of the universe is impossible.
1) It would require the matter in the "past" to dissapear, and move to the "future". Matter can not dissapear.
The only rules we have in this universe is "matter/energy can neither be destroyed nor created", time travel breaks those rules.