Introduction

Abstract

The physics of granular materials deals primarily with macroscopic objects. The term “macroscopic” means here that the objects making up such materials must at the very least be visible to the naked eye. This is in contrast to mesoscopic or microscopic media. As it turns out, the very concept of granular material imposes some further restrictions, raising the low end of the range somewhat above the limits of our visual acuity. It is important to realize from the outset that the physics of such objects has in most cases nothing whatsoever to do with the notion of temperature, at least not as we normally understand it. To appreciate this, we need only calculate the kinetic energy Ek of a small bead of silicate glass—a basic component of river sand. As we will see shortly, the physics of dry granular materials of the type we are interested in involves objects that are typically 100 microns (µm) in size or larger.