If you can send messages back in time, then someone can build a robot that can accept messages from the future, and kill your parents that way^. Sending informa

If you can send messages back in time, then someone can build a robot that can accept messages from the future, and kill your parents that way^. Sending information back in time is a paradox. Period Not quite. You're neglecting quantum mechanics. Very roughly speaking, in quantum field theory, the probability of an event happening is a weighted sum over all the possible ways that it could happen (a path integral), and (again, speaking roughly) the options that seriously violate the various conservation laws tend to have negligible contributions. Presumably the path integral formulation would still hold up even with closed timelike curves (time travel curves). An inconsistent state, like one where you kill off your own parents, would probably exhibit all sorts of self interference that would make its contribution to the path integral very small, whereas the consistent states would be much better represented, and much more likely to happen. Weird "violations" of physics could quite easily present themselves as the most probable outcomes, especially if the alternative was an inconsistent outcome. A good way to think about this is in terms of waves on a string, or the "wave" of an electron in orbit around a nucleus - the only vibration frequencies that "survive" are the ones that reinforce themselves, and the rest get cancelled out by interference (in the electron case, because they don't "match up" when they meet themselves after an orbit). If you think of the state of the universe as the electron, and the orbit as a loop through the closed timelike curve, then it's easy enough to imagine quantum mechanics doing all the hard work for us, and making sure that only consistent outcomes are reinforced, while all the other ones are destroyed by interference.