Time, Entropy, Coarse-Graining, Causality, and Life
Year: 2026
Type: preprint
Abstract: The fundamental laws of physics are generally time-reversible. In contrast, the second law of thermodynamics is time-irreversible with respect to macroscopic variables, establishing a link between the arrow of time, entropy growth, coarse-graining, and causality. These are all indispensable prerequisites for life, which is a macroscopic physical process that is necessarily time-irreversible, scale-irreducible, entropy-sensitive, and causally driven. We consider these questions within the axiomatic framework of causal set theory and formulate the law of conservation of causality in terms of fluid dynamics. Its corollary is the principle of causal equivalence, which states that there is no causally preferred scale of observation with respect to conservation laws. Nevertheless, scale still matters. A perfect observer like Laplace’s demon capable of tracking the behavior of matter with unlimited precision at the atomic scale might not detect any signs of life in the universe. Instead, we can agree that life, causality, and the second law of thermodynamics, with their time-irreversible processes, are manifested at macroscopic scales, but nothing of this sort, nor even the arrow of time, exists at the microscopic scales.
Source: Preprints.org
Author: Sergey B. Yurchenko
Language: English
Subfield: Statistical and Nonlinear Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7203929657