> I thought the Novikov conjecture postulated that time-travel would change nothing at all Not exactly, from the wiki article: > The simplest way to impose th

> I thought the Novikov conjecture postulated that time-travel would change nothing at all Not exactly, from the wiki article: > The simplest way to impose the principle of self-consistency in quantum mechanics (in a classical space-time) is by a sum-over-histories formulation in which one includes all those, and only those, histories that are self-consistent. So it is possible to change the past, but only in ways that are self-consistent and don't give rise to paradoxes. Regarding the ramifications for free will: > Novikov supports this point of view with another argument: physics already restricts your free will every day. You may will yourself to fly or to walk through a concrete wall, but gravity and condensed-matter physics dictate that you cannot. Why, Novikov asks, is the consistency restriction placed on a time traveler any different?