Granular materials are so widely-used that understanding their physics is very important. Clearly, something very special is happening at the moment when grains pack together in this way.
- Stefano Martiniani
At the moment they come together, the individual grains in materials like sand and snow appear to have exactly the same probability of combining into any one of their many billions of possible arrangements, researchers have shown.
The finding, by an international team of academics at the University of Cambridge, UK, and Brandeis University in the US, appears to confirm a decades-old mathematical theory which has never been proven, but provides the basis for better understanding granular materials – one of the most industrially significant classes of material on the planet.
A granular material is anything that comprises solid particles that can be seen individually with the naked eye. Examples include sand, gravel, snow, coal, coffee, and rice.
If correct, the theory demonstrated in the new study points to a fact of remarkable – and rather mysterious – mathematical symmetry. It means, for example, that every single possible arrangement of the grains of sand within a sand dune is exactly as probable as any other.
The study was led by Stefano Martiniani, who is based at New York University but undertook the research while completing his PhD at St John’s College, University of Cambridge.
“Granular materials are so widely-used that understanding their physics is very important,” Martiniani said. “This theory gives us a very simple and elegant way to describe their behaviour. Clearly, something very special is happening in their physics at the moment when grains pack together in this way.”
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Image: A huge range of materials are classified as granular – including sand, gravel, snow, nuts, coal, rice, barley, coffee and cereals. Globally, they are the second-most processed type of material in industry, after water.
Credit: Wikimedia Commons
Reproduced courtesy of the University of Cambridge
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