When one or two particles strike a smooth wall at normal incidence, they rebound in the direction whence they came. Yet, as we show here, a dense stream of non-cohesive particles hitting a target retains its integrity and deforms into a thin sheet with a shape resembling the structures created by an impinging liquid jet. However, with the granular materials, this “liquid” has special property of zero surface-tension. Furthermore, by decreasing the number of particles inside a jet, we can turn the behavior of the granular jet from the liquid-like behavior back to the normal particle-like behavior. We believe that this experiment is the classical analog of the much more microscopic and exotic experiment done at the Brookhaven National Laboratory, where the quark-gluon plasma produced by the high-energy collisions of gold ions also shows the liquid-like scattering pattern, similar to what we observed with granular materials.

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1. •Xiang Cheng, German Varas, Daniel Citron, Heinrich M. Jaeger and Sidney R. Nagel, “Collective Behavior in a Granular Jet: Emergence of a Liquid with Zero Surface Tension”, Phys. Rev. Lett. 99, 188001 (2007). pdf