The mysteries of sand
I mean of course granular media which also includes
powders, rice, asteroids and my favorite:
They have so many funny and yet unexplained effects!
Think just about size segregation: You put a large red sphere
on the bottom of a recipient filled with smaller blue ones, shake it
and after some the big one is on top.
The figure shows the starting of a simulation
of this "Brazil nut effect" made with
Jason Gallas , Thorsten
Pöschel and Stefan Sokolowski (J. Stat. Phys. 82, 443-450 (1996)).
next picture shows what happens after some CPU-time has been spent.
For more detail see our paper .
On granular materials I have also written several review articles
proceedings for the school in Altenberg published in Physica A,
Vol 313. 188-210 (2002) or an article with
Stefan Luding published in Continuum Mechanics and Thermodynamics,
Vol.10, 189-231 (1998) and popular articles in several languages
including english ,
german , spanish ,
portugese and corean .
And here comes the largest sand grain I have ever seen (in Mamallapuram close to Chennay):