What happens if time goes backwards?

if the contraction force exceeds the expansion force, time can probably go backwards.Personally, I understand this question as "what will happen to irreversible processes, such as heat conduction, for example, if you turn back time?" All reasoning about entropy, in fact, is in a sense sucked out of thin air. Where did entropy come from? From thermodynamics. It arose along with pressure, volumetric energies, and so on. As a result, from the same thermodynamics, irreversible equations of the type of heat conduction, the postulate of an increase in entropy, were obtained. But the original problem was Hamiltonian, that is, reversible in time. The original quantum problem, for that matter, was also time reversible. Maxwell's equations are also reversible in time if B is replaced by -B. All irreversibility appeared from the fact that it is simply impossible to average the original problem as simply as it is done in thermodynamics, due to the fact that instead of solving exactly the equations of motion of all particles, averaged characteristics were written. That is, of course, in thermodynamics everything is done "correctly", and everything agrees with the experiment, but only up to those insanely unlikely states when, as in a well-known problem, all gas molecules can one fine moment climb into the right half of the vessel, and leave the left free. Therefore, time can be turned back, at least not in the entropy problem. Problems may be that not every problem can be written in a reversible Hamiltonian or Lagrangian form. I can't say anything for elementary particle physics and other near-string sciences, but even in classical electrodynamics, by and large, this cannot be done. But this is not entropy, but something else.