Physics 540 Fall 2005

Prof. Peter Stephens received the following letter from a person with a BA degree in physics.  He thought the physics 540 class might be interested.  It is an illustration of the 4th law of thermodynamics: "the desire to violate the second law is unconquerable."

Dear Professor Stephens:

I would like to share with you some ideas about thermodynamics. I have already sent my ideas to several physicists and they all have responded with stupendous enthusiasm.

I believe there are grounds for the Second Law of Thermodynamics to be violated. These grounds have to do with a liquid-vapor equilibrium. If the molecules of the vapor have a higher average kinetic energy than the molecules of the liquid, then gravity is separating higher speed molecules from lower speed molecules. This suggests that gravity can decrease the entropy of a fluid.

If the molecules of the vapor have the same average kinetic energy as the molecules of the liquid the Second Law won't be violated. A simple experiment can test the law in this regard. The experiment is as follows. Set up a liquid-vapor equilibrium with a movable partition at the liquid-vapor interface. Let this partition have one or more sizable holes (so that the system would be in equilibrium). Cover the holes. If the average kinetic energy of the molecules of the vapor is greater than
that of the molecules of the liquid, there will be an energy flow from the vapor to the liquid. The liquid would then expand and the partition would rise. Mechanical energy could be obtained. Next the holes of the partition could be opened. Presumably the system would return to its original configuration. The Second Law would be violated.

I invite you to comment.