Ah yes, this is talking not only about time travel to the past, but to the future as well. However this is flawed almost immediately. In the theory that every event is predetermined and therefore creating a single line which time follows, thus denouncing free will, a person who travels to the future would not be able to meet his older self because that person would not exist. If Mr. X travels one day into the future to meet himself, that would mean he would not exist in the world for exactly one day because he would be traveling to the future. He would reappear to find that he was gone for a day and that would be it. However time does not flow in a single straight line, we only perceive it that way in this dimension. Every "choice" that we individuals make shapes the fabric of time and creates the dimension in which we live. Lets call this dimension in which you are reading this sentence dimension A. You may reject this theory and decide to post a new comment disproving it. You may accept this theory and decide to post nothing. You may read this and decide to leave the forum and so on... Whatever decision you decide on has just created a new dimension where you did this differently. Now there are approximately 7,000,000,000 people on earth at any given moment, so lets assume that half are awake and active at any given time so 3.5 billion. We can safely assume that each person makes at least 1,000 decisions a day (this number should be significantly higher). That would mean that 3.5 trillion decisions are made every 24 hours. The number of universes able to be created is nearly too large to count (you can use the permutations formula to figure out this number). This same theory is also the reason time travel is so tricky. If a person were to go into the past (meaning he travels back through the events of dimension A) he could then alter the past. However, on his return home one of two possible outcomes will occur:
1. He will be transported back to the present dimension A where everything is as it was before he left and nothing has changed (his changing of the past has now altered a different dimension where he was transported through time.)
2. He will move down one out of trillions of new paths leading to new dimensions that all start at the point that he altered.
To put outcome 2 more simply, imagine that you have a tree which represents time and people's decisions. Starting at the base of the trunk and moving up you paint a single branch orange, but you only follow one branch until it ends at a single leaf, this is dimension A. By changing the past you have created new branches that start at whatever part of the tree you changed and have now eliminated the orange branch all together. You are now forced to paint a new branch starting at whatever point was changed and follow it. This new branch you have followed is one new dimension which has been created due to your medaling of the past. If one were to travel to the future the same thing would occur. The person would appear in a time where he has not existed since the time that he transported.