Physical Review Focus

Physical Review Focus is a FREE APS electronic journal featuring selections from Physical Review Letters explained at a level accessible to all physicists. The editor is David Ehrenstein [see April 1998 APS News]. APS News is printing samplings from PR Focus to introduce the membership to this new journal. To receive one-paragraph introductions (such as the one below) each week by e-mail, send a blank message to join-focus@aps.org, or go to the list.

Antigravity in a Sandbox

Fancy Flows. Shinbrot and Muzzio found these unusual flow patterns when they titled the bed of sand.Troy Shinbrot/Rutgers University

Large objects seem to defy gravity in a shaking box of sand, according to a report in the 16 November PRL. The authors found that with vigorous shaking, heavy objects placed in the sand float to the top, while light objects sink. They propose a partial explanation for the phenomenon but admit to being puzzled by some of their observations. The experiments provide an example of the surprisingly complex behaviors physicists have seen in granular materials, which do not obey standard equations for either fluids or solids. (Phys. Rev. Lett. 81, 4365; see the complete PR Focus story, including videos, posted online 23 November 1998.)