The hypothetical physics of heat, energy, and work operating in reverse temporal direction. In retrothermodynamics, heat would
flow spontaneously from
cold objects to hot ones, friction would accelerate objects instead of slowing them down, and engines would run by absorbing exhaust fumes and fuel while outputting work and
air. It's what you'd get if you took a video of
normal thermodynamic processes and played it backward—a universe where every energy transaction is perfectly reversed, and the arrow of thermal time points the other way.
Retrothermodynamics (
Physics) Example: "The movie scene where a
character's breath unfreezes and returns to their
mouth is a charming moment of cinematic retrothermodynamics."