I really like this theory: http://lesswrong.com/lw/fok/causal_universes/ http://lesswrong.com/lw/fok/causal_universes/ But regardless, what would it even mean

I really like this theory: http://lesswrong.com/lw/fok/causal_universes/ http://lesswrong.com/lw/fok/causal_universes/ But regardless, what would it even mean for there to not be an arrow of time? Such a universe would have egg shells on the floor, and then waves of energy that just happen to hit the eggshells, at just the right velocity to propel each piece to assemble an unbroken egg. What a remarkable coincidence that would be. It would be very difficult, perhaps impossible, to make a universe like that. IMO it's just like cellular automata. You start with a "start state" of something simple or random. Perhaps just a single cell. And then it evolves into complex patterns as each time step causes the next time step. There are reversible cellular automata, that in theory don't have an arrow of time either. You could start at any state, and reverse it, just as easily as advance it. But unless you are remarkably clever, or lucky, at arranging the start state, it will tend to increase in entropy over time. Or rather, as the step counter increases.