There exists Green's Functions such that the solutions appear to be retro-causal. The Klein-Gordon equation allows for antiparticles to propagate backwards in time. Does this mean the future can influence the past and present? Then again The Poincare Recurrence Theorem states that over a sufficiently long enough time a dynamic system will return very close to its initial conditions. Is it possible that Poincare Recurrence Time can be reconciled with Green's Functions with non-zero values at negative t such that the function is describing a recurrence in the system? In other words could antiparticles be artifacts of a Poincare Recurring Universe pre-dating the big bang?