Here is a recording of Professor Jim Al-Khalili of Theoretical Physics and Chair in the Public Engagement in Science at the University of Surrey giving a lecture on time travel separating the facts from fiction. Its a bit long but it is a great lecture and he really breaks it down.
https://www.youtube.com/watch?v=DoJU3GxkuYw
https://www.youtube.com/watch?v=DoJU3GxkuYw