This season, Game Of Thrones introduced a time-travel element to the show. Bran, through his training with the Three-Eyed Raven, is now able to move around in time. What he can’t do, however, is change the past in such a way that it would change the future. Which raises the question: How does time travel work on Game Of Thrones? Thankfully the folks at Vox have put together a video explaining it.
Basically, there are three types of fictional time travel: the multiverse timeline, the dynamic timeline, and the fixed timeline. Most fictional time travel takes place in either a multiverse or dynamic timeline. (A multiverse timeline is one in which each choice you make in the past creates an alternate future, like in Doctor Who. A dynamic timeline is one in which your actions can affect the present you came from, like in Back To The Future.)
Game Of Thrones, though, is doing a different version of time travel. You can’t do anything in the past that would change the present you came from. You can’t kill your grandfather, because you exist. Anything you do in the past will only confirm things in the future, like accidentally frying young Hodor’s brain. It’s called a “closed timelike curve” in mathematical physics. But to borrow a phrase from another HBO show, it’s almost like time is a flat circle.