@article{Frampton2009WhatIT,
title={What is the entropy of the universe},
author={P. Frampton and S. Hsu and T. Kephart and D. Reeb},
journal={Classical and Quantum Gravity},
year={2009},
volume={26},
pages={145005}
}

Standard calculations suggest that the entropy of our universe is dominated by black holes, whose entropy is of order their area in Planck units, although they comprise only a tiny fraction of its total energy. Statistical entropy is the logarithm of the number of microstates consistent with the observed macroscopic properties of a system, hence a measure of uncertainty about its precise state. Therefore, assuming unitarity in black hole evaporation, the standard results suggest that the… CONTINUE READING