Shannon's Measure of Information and the Thermodynamic Entropy

This lecture is concerned with two topics: First, we discuss the widespread confusion between a descriptor of the state of the system, and changes in the states in a spontaneous process, on one hand, and a descriptor of entropy on the other hand. The second, is concerned with a clear distinction between Shannon's Measure of Information (SMI), and the Thermodynamic Entropy. The first is defined on any distribution, and therefore it is a very general concept. On the other hand Entropy is defined on a very special set of distributions. Therefore it is suggested that this conference will be called MaxSMI rather than MaxEnt. Next we show that the Shannon measure of Information (SMI) provides a solid and quantitative basis for the interpretation of the thermodynamic entropy. For an ideal gas the entropy measures the uncertainty in the location and momentum of a particle, as well as two corrections due to the uncertainty principle and the indistinguishability of the particles.