Retromechanics (Physics)

A speculative branch of physics concerned with mechanical systems operating under time-reversed conditions. If you could reverse time, Newton's laws would still hold (they're time-symmetric), but every collision, every trajectory, every mechanical interaction would play out backward. Retromechanics describes this reversed world: balls un-bouncing, pendums unsweeping, planets un-orbiting. It's a useful thought experiment for understanding why the Second Law of Thermodynamics (which isn't time-symmetric) gives time its direction, even though the underlying mechanics don't care which way the clock runs.

Retromechanics (Physics) Example: "The simulation showed planets orbiting backward, demonstrating retromechanics—gravity doesn't care about time's direction, even though everything else does."

by Dumu The Void March 11, 2026