Every year, the world consumes around 50 billion tonnes of sand, gravel and crushed stone. The astonishing scale of this demand is hard to comprehend—12.5 million Olympic sized swimming pools per year ...

A: We don’t know. No one understands how sand works. That may sound absurd, but it’s sort of true. Understanding the flow of granular materials like sand is a major unsolved problem in physics. If you ...

Understanding how grains flow is vital for everything from landslide prediction to agricultural processing, and scientists aren’t very good at it. By Randall Munroe What is the softest sand in the ...