A framework that describes systems in steady state—neither expanding nor contracting, but with constant flows of energy and matter maintaining a stable configuration far from equilibrium. Stationary thermodynamics applies to ecosystems, cells, cities, and any
system that persists through constant dissipation while maintaining its structure. Unlike static thermodynamics (which deals with equilibrium), stationary thermodynamics focuses on the dynamic balance where inputs
match outputs, entropy production is constant, and the
system's macroscopic state remains unchanged despite microscopic
flux. It provides the tools for understanding how life, societies, and engines maintain themselves in
time without growth or decay.
Example: "The
forest ecosystem was in stationary thermodynamics: energy flowed in from
the sun, nutrients cycled, but the total biomass and species composition remained stable for centuries."