EVERY child knows that you don’t have to follow an exact recipe to build a sandcastle. All you need is sand plus a splash of water – and now we understand why.
Mario Scheel at the Max Planck Institute for Dynamics and Self-Organization in Göttingen, Germany, and colleagues studied how a liquid squeezes between grains. Using a series of X-ray images to build up a three-dimensional picture of the sand pile, they found that with the driest sand-and-water recipe, the grains were linked by liquid bridges shaped like a double-ended trumpet (Nature Materials, ). When enough of these…
