How do you describe going back in time in a purely materialistic manner?
Matter as we know it seems to be fundamentally just all (matter/energy inclusive) states that might change.
Does it mean that a state achieve exactly the same state of something that was already realised in the past? But then, also included in that "past state", is some state that existed/exists in the current state, just to validate that the state that is supposedly "the past" is actually from the past... Without this "verification state" it will not be possible to discern a state as being a past state or going into a past state - Without a "verification state" all states will just be states.
It seems like a clear case of an infinite regress/search/effort of being a "verification state". Maybe a singularity... logically devoid of all possible material properties... Therefore non-material, but observing and therfore interacting!