Irreversibility as thermodynamic time

In Newtonian mechanics, time and space are perceived as absolute entities. In Einstein’s relativity theory, time is frame dependent. Time is also affected by gravitational field and as the field varies in space, time also varies throughout space. In the present article, the thermodynamic-based time is investigated. In macroscopic view of thermodynamics, energy is conserved in every system or process. On the other hand, exergy (availability) is not conserved and can be destroyed, and “irreversibility” is generated. Since each thermodynamic system may generate different amounts of irreversibility, this quantity is system dependent. The present article investigates the characteristics of entity irreversibility. (1) It is found that the entity behaves in the similar manner as the clock time in the standard configuration of inertial frames under Lorentz transformation. (2) It is also found that the entity is affected by gravity fields in the similar manner as the clock time. We have demonstrated that, like clock time, irreversibility is frame dependent, and affected by gravity in the similar manner as the clock time. For these reasons, we propose to call the of the system as the thermodynamic time. The time’s arrow is automatically satisfied, since irreversibility generation always proceeds in one direction (toward future). Based on the strength of the findings (1) and (2), a possible application of the irreversibility is an interpretation and management of the aging of biological systems. It is shown by other authors that entropy generation (equivalent to irreversibility) is a parameter for the human life span. Our sensation of time flow may be attributed to the flow of availability and destruction of it through the living system.