Two bodies initially at different temperatures gathered into an isolated container exchange heat and reach an equilibrium state with a common final temperature. During the process, the system is out of equilibrium and its intermediate temperature is not well defined. By conceiving a quasi-static process with infinitesimal steps from the initial to…

It is well known that heat transfer between two objects results in a positive change in the total entropy of the two-object system. The second law of thermodynamics states that the entropy change of a naturally irreversible process is positive. In other words, if the entropy change of any process is positive, it can be inferred that such a process…

This is a companion to our previous paper in which we give a published example, based primarily on Perry's work, of a graph of ln "y" versus "t" when "y" is an exponential function of "t". This work led us to the idea that Lord Kelvin's (William Thomson's) estimate of the Earth's age was…