I'm not exactly sure where to put this question, so admins feel free to move it. I have been reading about Conway's game of life, and learned about the halting problem. Basically, you can reach states in the game that are irreversible. Basically, the conditions at any point in time, in general, won't give you enough information to reproduce the previous steps. Simplest example: you have one cell, and it dies, so you are left with an empty board. That empty board can't tell you there was once one cell. Is this also the case with reality? Are there states that systems can reach which are not reversible (as in not rewindable)? Basically a state that cannot tell you about the past of the system. If so, then is that the nail in the coffin for time travel to the past? Either that or if you go into the past, it wouldn't be "complete". Any thoughts on this?