Clausius Defined Entropy, Showing It Always Increases in Irreversible Processes and Stays Constant in Reversible Ones Like Carnot's Ideal

While entropy isn't directly measurable, derived quantities are. Schrödinger (1944) linked life to negentropy, suggesting life maintains order by consuming energy and reducing local disorder. To understand this, Dyson's toy model of a cell, a Markov chain with three equilibrium states including 'life' and 'death, offers a framework.

Boltzmann quantified entropy as the logarithm of the number of possible states times the Boltzmann constant, a simple yet non-obvious result. For example, in Curie's model of a magnet with five atoms and energy E=1, three spins up and two down yield 10 possible configurations.