University of Chicago physicists have created a novel state of matter using nothing more than a container of loosely packed sand and a falling marble. They have found that the impacting marble produces a jet of sand grains that briefly behaves like a special type of dense fluid.Needing very fast, non-invasive tracking of the interior of the sand, the group used used high-speed x-ray radiography taken at 5,000 frames per second, the fastest ever at the Advanced Photon Source.