Researchers at the University of Twente in the Netherlands have created an experiment that demonstrates how sand can exhibit liquid-like properties. They provide beautiful photos and a 1k-frame/sec movie of a marble-size steel ball dropping onto loose, fine sand. This may aid geophysicists in understanding what happens when an asteroid smashes into a planet.
This reminds me of attempts in the 1970’s in graduate school and at my first job at a R&D organisation to use computers to model the flow of fluids. It was simple when we tried simple things–rivers and streams, waves in very deep water, hydraulic jumps, etc. Proved impossible for anything “complex”. 99% of fluid flows are “complex”. This movie helps me appreciate why.