Charles Radin
Equivalence between random close packing in granular matter and 
freezing in the hard sphere model
(764K, pdf)

ABSTRACT.  The notion of random close packings of a 
bulk static collection of ball bearings or sand grains was introduced 
in the 1960's by G.D. Scott and J.D. Bernal. There have been numerous 
attempts to understand the packings. We give a short argument, 
following an earlier paper on liquids by Bernal, which explains the 
packings in purely geometric terms.