I beg to differ, unfortunately. Don't you think Hitler would have been killed and events like Pearl Harbor and 9-11 stopped, if time travel was discovered 1000 years from now? That alone leads me to believe that nobody will ever discover time travel on our planet. People like JFK just wouldn't be dead if someone could go back and fix it. Now, if alternate dimensions exist for every variable of time, there's still a chance that time traveling can be discovered. If not - I'm thinking it won't ever be. Unless you're John Titor, of course. If someone did go back and change those events no one would ever know, except the person that changed them. To everyone else those things never would have happened.