"Fun in the Sand: Some experiments in granular physics"

http://www.phys.psu.edu/~schiffer/

In the last two decades, condensed matter physicists have begun an intense study of the dynamic and static properties of granular media (materials made from individual acroscopic solid grains). These materials offer a vast arena of new physical phenomena which are highly accessible and largely unexplored. I will discuss recent work on three different physical phenomena in granular media which demonstrate how relatively simple measurements in this area can reveal surprising results. 1). How interstitial liquid between the grains affects granular properties and leads to the development of correlations between the grains. 2). How grains pack when you heat them up and cool them down. Although grains are macroscopic and not affected by thermal fluctuations, careful measurement shows that the process of heating and cooling them does affect them through irreversible changes in packing. 3). How the motion of an object being pulled slowly through a granular medium is resisted by the “jamming” of grains, resulting in a drag force which differs dramatically from viscous drag in a fluid both in its average properties and in having large fluctuations.