The Impossibility of Time Travel

Gillis: If we don't have extra time dimensions, then time travel cannot change the past. And what are the chances our universe would be built with extra time dimensions just in case someone wanted to come along? It's possible you can build a video game with that, but for a spontaneously arising universe, it doesn't seem very lightly. So if you want to see more of me and check out me playing Portal Reloaded,. That's the fan sequel to Portal 2 with an extra time portal.