irreversibilitas

Irreversibilitas, or irreversibility, is a property of a process in which the initial state cannot be exactly recovered from the final state without external intervention. In everyday language, it denotes a directional change that leaves lasting effects and cannot simply be undone by retracing steps. The concept appears across sciences, philosophy, and information theory, often tied to the idea of time’s arrow and the unidirectional progression of certain transformations.

In thermodynamics and physics, irreversible processes include friction, viscous dissipation, heat transfer across a finite temperature gradient, and chemical reactions that proceed predominantly in one direction. The second law of thermodynamics states that the total entropy of an isolated system tends to increase, which underpins the observed asymmetry of many natural processes. Although the fundamental laws governing microscopic dynamics are time-reversal symmetric, irreversibility emerges at macroscopic scales through statistical behavior: many more microstates correspond to high-entropy configurations, making the backward path statistically unlikely.

In information theory and computation, some operations erase information irreversibly, dissipating energy in the process in accordance with Landauer’s principle. This has motivated interest in reversible computing, which aims to perform computations with minimal energy loss by using operations that can be inverted.

In philosophy and cosmology, irreversibility relates to debates about time’s asymmetry, causality, memory, and the evolution of systems such as the universe or radioactive decay, where certain transitions are effectively one-way on observable timescales.

See also: entropy, arrow of time, reversibility, Landauer’s principle.