I had a thought that I wanted to run by physicsforums so all of you can tell me that I'm wrong and make me feel better. One of the main issues with the concept of time travel into the past is that we don't know whether is breaks any physical laws in the process. Here is what I believe might be a law that backwards time travel actually breaks: Suppose you are examining a particle at one point in time. At that point in time, you figure out that particles momentum. Then, you hop in your time machine, and travel back in time, and measure the particle's position at the exact time the you measured its momentum. Wouldn't that suggest that backwards time travel can break Heisenburg's Uncertainty principle?