Retrophysics

The umbrella term for any branch of physics that describes phenomena as they would appear if time ran backward. It encompasses retrothermodynamics, retromechanics, retroentropy—the whole suite of physical laws operating in reverse chronological order. Retrophysics is a powerful tool for thought experiments, helping physicists understand why certain processes are irreversible even when the underlying equations are time-symmetric. It's the physics of the rewound tape, the universe played backward, the cosmic movie running from credits to opening scene.

Example: "The professor assigned a retrophysics problem: calculate what the solar system would look like if we ran the equations backward for a billion years."

by Dumu The Void March 11, 2026