What if you went back in time and killed your own grandfather? Would you still be born? Or would you have thus killed yourself? Thanks to Google #sciencegoals for sponsoring this video! Link to the previous MinutePhysics video: https://www.youtube.com/watch?v=XayNKY944lY If you could travel back in time, and you killed your grandfather, would you be killing your future self? What do physics, complexity theory, and computer science have to say about this famous murderous time-travel paradox? Scott Aaronson Notes that discuss time travel and computation, computational complexity, closed timelike curves, and the grandfather paradox: http://www.scottaaronson.com/democritus/lec19.html Technical paper that discusses the same thing: http://arxiv.org/abs/quant-ph/0502072 Thanks to everyone who supports MinutePhysics on Patreon! http://www.patreon.com/minutephysics Link to Patreon supporters here: http://www.minutephysics.com/supporters.html Music by Nathaniel Schroeder, http://www.soundcloud.com/drschroeder MinutePhysics is on Google+ - http://bit.ly/qzEwc6 And facebook - http://facebook.com/minutephysics And twitter - @minutephysics Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Created by Henry Reich