Liquid Sand

Mark Trodden in Cosmic Variance:

One of the more fun physics stories that I’ve seen recently is from an area of research quite removed from my own, but that I have found fascinating for a while now. I have been fortunate to have excellent condensed matter colleagues at both my recent institutions, and quite a number of them are interested in soft condensed matter – classical physics that describes the behavior of large numbers of particles, far from equilibrium, often when entropic considerations dominate the dynamics.

The field covers such diverse systems as the behavior of biological membranes and the dynamics of grain in silos, and contains many examples in which nontrivial geometry and topology lead to the possibility of discovering new phenomena that, unlike in my own field, can increasingly often be checked in a laboratory experiment designed and built in a relatively short time.

The story that caught my eye (via Wired Science) recently concerns the behavior of a system that is so simple that you would think we know all that there is to be known about it – falling sand.

In the video above, a stream of sand is allowed to fall over several feet, and is filmed using a high speed video camera that falls at the same speed as the sand. The result, as you can see, is that the sand forms “droplets” just as water would, even though most people would not think of granular materials as anything like a liquid.

More here.