I'm working on a time travel novel, and I've run into a few problems that I haven't been able to work out so far. Part of the plot is that the characters only travel through time in a set time period of around 10 years. The problem is how do I make is so that the characters never have to worry about running into themselves if they travel back to the same time and place. One idea I've come up with is that the laws of physics don't allow for the creation or destruction of matter, so if a time traveler were to travel back in time to a time in which he already exists then his past self just doesn't exist anymore. Only one copy of every person can exist at one time. Does this make sense or is there a better way I could make this work?