I do not pretend to be a genious mathematician, but the theories discussed here intrigue me. I would imagine that majority of people who come to this forum are very familiar with Dr. Kaku's work, and similar work of other scientists. My question is, can past or future be altered? You see, in my opinion, neither one can be altered. The future has already happened. And no matter what we do to prove that we guide our own live (which we do), the future has already been decided, not necessarily for us, but by us. If we consider time to be just another dimension complementing the other three, than consider the following example. When you are riding in a train, the scenery in your view changes since you are moving along the axis. If you can't see the building that is one mile away from you, it doesn't mean it does not exist. Our travel in time that we partake in every second, is similar to the above travel in a train. The view in front of us changes constantly over time since we are moving along the time axis. But the fact that we cannot see what will happen one year from now, does not mean it does not already exist. Thus, if time is just another dimension, it should be possible for us to travel back and forth through time. But whatever is going to happen, has already happened and we are powerless to alter the events.