One of my characters will be "splitting" time when he goes back to try to change the past, consequently causing much havoc to other's lives. This separate time-track will split space and change the present and the past and create a closed time loop. This brings up all kinds of issues that I look forward to working on shortly!
I have discovered that it is much harder to time travel to the past then to the future. So many more issues are involved. You begin to worry about such things as Time Police; that some unknown force will stop the passage as it is not allowed by the natural rules of our universe.
You begin to understand that space time in not intuitive--that most things that seem logical on Earth are not 'logical' in our galaxy. It's like learning to 'think' all over again and I could not be more fascinated. . .