A brief introduction to granular media, with emphasis on the implications for the geometry of sphere packing.

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An experiment on dilatancy:

M. Schröter, S. Nägle, C. Radin and H.L. Swinney, Europhys. Lett. 78 (2007), paper 44004

A theory of random close packing:

C. Radin, J. Stat. Phys. 131(2008) 567-573

Monte Carlo simulations of random loose packing:

D. Aristoff and C. Radin, preprint, University of Texas, 2008