Standard and derived Planck quantities: Selected analysis and observations

We provide an overview of the fundamental units of physical quantities determined naturally by the values of fundamental constants of nature. We discuss a comparison between the “Planck units”, now widely used in theoretical physics, and the pre-quantum “Stoney units” in which, instead of the Planck constant, the charge of the electron is used with very similar quantitative results. We discuss some of the hindsight physical motivation for such units, and also put forth a summary of the arguments supporting various cases for making specific physical interpretations of the meanings of some of these units. The new aspects we discuss are a possible physical basis for the Stoney units, their link to the Planck units, and also the importance of Planck units for thermodynamical quantities in the context of quantum gravity.