The cracks that radiate from a hole in a broken window (pictured) reveal quantitative information about the shattered material and the projectile that smashed it.

Credit: ISTOCKPHOTO/THINKSTOCK

Nicolas Vandenberghe and his colleagues at Aix-Marseilles University in France studied such cracks by firing bullet-shaped steel cylinders at sheets of glass and plastic. The team used a high-speed camera to show how the cracks formed and spread. The number of radial cracks increased with the impact speed, as well as the material's brittleness. The group developed a mathematical model that accounted for these observations. This model could be relevant on Earth and in space — helping forensic investigators to reconstruct crimes, and helping astrophysicists to analyse impact craters on distant planets and moons.

Phys Rev. Lett. 110, 174302 (2013)