Is an "anti-universe" possible? By anti-universe, I mean a universe where anti-matter dominates over matter and the direction of time is reversed. My understanding is that one interpretation of antiparticles is that they are the same as regular particles going backwards through time. If a universe contained predominately anti-particles, would time run in reverse? A related question: Is it possible that an anti-universe was created from the same big bang that created our universe? The lack of antimatter in our universe may be a result of antimatter going into the anti-universe at the big bang. Time for the anti-universe would be reversed and logically the second law of thermodynamics would also operate in reverse. It has been about 14 billion years since the big bang. The anti-universe would have been at a similar state to our present universe 14 billion years before the big bang. I have not seen any speculation in this area. Has anyone looked into the theoretical possibility of an anti-universe?