Part two of a short video by science journalist Dan Falk, author of In Search of Time (Macmillan 2008).
Time travel into the future is relatively easy—forgive the pun—but what about travelling into the past? Though nothing in the laws of physics prohibits it, such a journey would seem to violate our notions of causality and free will. And then there’s the Grandfather Paradox, which physicists and philosophers have grappled with for more than a century. (10 min.)