Speed-Dependent Weighting of the Maxwellian Distribution in Rarefied Gases: A Second-Law Paradox?

摘要

We show that the velocity distribution in rarefied (i.e., Knudsen) gases is spontaneously weighted in favor of small speeds away from the Maxwellian distribution corresponding to the temperature of the container walls—despite thermodynamic equilibrium with the walls. The consequent paradox concerning the second law of thermodynamics is discussed.