To better understand the ways in which grains move and organize themselves, it would be helpful to minimize gravitational interactions so that only inter-grain and grain-wall interactions were important.

To achieve this, French researcher Eric Falcon, Ecole Normale Superieure, and colleagues resorted to outer space, where they performed the first experiment with vibrated granular media in a low-gravity environment, according to the American Institute of Physics Physics News Update Number 438.

On board a sounding rocket, inelastic frictional collisions among the grains themselves and with the container walls were the only interaction mechanisms at work.

Once fluidized (agitated), the grains formed a uniform gas. But at higher densities, the grains formed dense, motionless 3-dimensional clusters surrounded by low-density regions. Details are spelled out by Falcon et al in Physical Review Letters, 12 July 1999.

12-Jul-1999