English

Is Entropy Associated with Time's Arrow?

Popular Physics 2017-05-04 v1 Statistical Mechanics

Abstract

We start with reviewing the origin of the idea that entropy and the Second Law are associated with the Arrow of Time. We then introduced a new definition of entropy based on Shannons Measure of Information, SMI. The SMI may be defined on any probability distribution, and therefore it is a very general concept. On the other hand entropy is defined on a very special set of probability distributions. More specifically the entropy of a thermodynamic system is related the probability distribution of locations and velocities or momenta of all the particles, which maximized the Shannon Measure of Information. As such, entropy is not a function of time. We also show that the H function, as defined by Boltzmann is an SMI but not entropy. Therefore, while the H-function, as an SMI may change with time, Entropy, as a limit of the SMI does not change with time.

Keywords

Cite

@article{arxiv.1705.01467,
  title  = {Is Entropy Associated with Time's Arrow?},
  author = {Arieh Ben-Naim},
  journal= {arXiv preprint arXiv:1705.01467},
  year   = {2017}
}

Comments

27 pages and 7 figures

R2 v1 2026-06-22T19:35:45.961Z