Number 286 (Story #1), September 13, 1996 by Phillip F. Schewe and Ben Stein PARTICLE-LIKE LOCALIZED EXCITATIONS IN A BED OF SAND can form into molecules and even crystals. University of Texas physicist Harry Swinney shakes an evacuated container of sand (actually a lake of tiny bronze balls ) up and down. At a certain frequency the energy put into the system manifests itself as small isolated heaps of sand (about thirty grains in diameter) which also bob up and down. These heaps, which Swinney calls "oscillons," are stable (holding together for thousands of shakings) and able to slowly drift across the sand bed. And just as with electrical charges, when it comes to oscillons opposites attract. As long as their centers are within 1.4 diameters of each other, oscillons of opposite phase (one at its peak height and one at its shallowest depth) can enter into a dipole state. These peak-crater pairs in turn were observed to form chains and other configurations including extended lattices. Swinney and his colleagues have no definite answer as to how and why the oscillons form and interact, but he feels that such localized structures may exist in other dissipative systems (systems which steadily lose energy), and not just in granular materials (see Update 264). (Paul. B. Umbanhowar, Francisco Melo, and Harry L. Swinney, Nature, 29 August 1996. Some associated figures can be viewed on our Physics News Graphics website: /png/)