Il silenzio e l’umanità autentica : antropologia ed etica fra Montaigne e Heidegger

During the long history of Western thought, silence has always represented the main condition for the development of a deep meditation about the Self. Through this activity, which could seem to be in contrast with social life and philosophical praxis, several thinkers have tried to reach the spiritual nature of human beings. However, when they had to assign a foundation to it, the same meditation, which had started from the same bases, brought them to opposite conclusions. The motive for this divergence is grounded on the fact that materiality is not the only component that constitutes silence, since it has indeed a complex nature and so it consists also of an immaterial part. In addition, this inner and more hidden aspect could only be perceived through a direct contact that is rarely and personally achieved. As a consequence of this complexity, beside an interpretation of silence as a manifestation of God’s voice and a proof of the transcendent peculiarity of human beings, another reading has developed along a parallel path. This interpretation has represented silence as an expression of an utterly immanent spirituality that characterizes humanity. Two authors, in particular, can exhibit this frequently forgotten second stream of Western thought that has unceasingly run from Hellenistic age to contemporary culture: they are Michel de Montaigne and Martin Heidegger. This essay seeks to rebuild this long and complex plot of the history of Western thought through the texts’ recourse. At the same time, it seeks to grasp, in the relationship between men and silence, some fundamental prerequisites that could be considered absolutely necessary in order to design an anthropology and, consequently, an ethics with the characteristics of a recovered authenticity. These two renovated categories, according to the immanent feature of silence, have their own justification exclusively in the voice of human conscience and their purpose lies precisely in the relationship with others.

Thermodynamics/dynamics coupling in weakly compressible turbulent stratified fluids

In traditional and geophysical fluid dynamics, it is common to describe stratified turbulent fluid flows with low Mach number and small relative density variations by means of the incompressible Boussinesq approximation. Although such an approximation is often interpreted as decoupling the thermodynamics from the dynamics, this paper reviews recent results and derive new ones that show that the reality is actually more subtle and complex when diabatic effects and a nonlinear equation of state are retained. Such an analysis reveals indeed: (1) that the compressible work of expansion/contraction remains of comparable importance as the mechanical energy conversions in contrast to what is usually assumed; (2) in a Boussinesq fluid, compressible effects occur in the guise of changes in gravitational potential energy due to density changes. This makes it possible to construct a fully consistent description of the thermodynamics of incompressible fluids for an arbitrary nonlinear equation of state; (3) rigorous methods based on using the available potential energy and potential enthalpy budgets can be used to quantify the work of expansion/contraction B in steady and transient flows, which reveals that B is predominantly controlled by molecular diffusive effects, and act as a significant sink of kinetic energy.