
		INTRODUCTION

We all like (or liked) to play with sand once in a while.  There-
fore  pouring,  shearing  or  vibrating of sand seem to be rather
familiar experiences.  Modern science,  however,  has  much  less
understanding for the motion of sand than for instance for fluids
(``hydrodynamics'') or solids (``e.g.  elasticity''):  while  for
fluids  and  solids  we can describe the velocities and displace-
ments by differential equations no such equations are  known  for
sand  or in general for ``granular media'' (This includes cement,
grains, asteroids, pills, rocks, gravel, etc.).  The  only  reli-
able way today to describe the motion of sand is a direct simula-
tion on the computer.

In this section we want to show how the behavior of sand  can  be
simulated  using  ``Molecular  Dynamics''.   Then we will present
various practical cases where easy hands-on experiments will also
be  proposed that can be performed in parallel.  We will investi-
gate how an hourglass works. We will see how we can get the  Bra-
zil  nuts  out  of  a mixture of nuts just by shaking, Further we
project the following applications: Avalanches  of  sand  down  a
dune,  convection  rolls  in  vibrating sand and density waves of
sand flowing through a narrow pipe.

/*
	MolecularDynamics;
	GettingStarted;
	Hopper;
	Vibration;
	Billiard;
