I do believe that we can go back in time.
Here's why:
Imagine Time and Space.
Imagine Space going left to right like threads.
Now imagine Time as a specific point, i.e. now. From that thare are infinite different ways something can happen, lime radii of a circle, and from a point in one strand there are infinite more strands (possibilities) THAT ALL HAPPEN, it just so happens that we live in one of those strands. Now if you lived in one strand of time, and somehow you managed to invent a time travel machine, you would go around that time-space continuum to that exact time where you want to go (that "point" where infinite possibilities are there) from there you can change things and go down ANOTHER STRAND, where everything is different. Your strand of time that you came from would go on without you, but the new one which you have created will be changed.