Video of the Week #103, August 1st, 2013:From:The Beautiful Science of Helicopter Halos by Kyle Hill at Overthinking It.
When a helicopter descends into a sandy environment, it creates a brilliant halo that is a stark contrast to the solemnity of battle. But scientifically, what are these miniature galaxies adorning helicopter blades? It's due to something called the the Kopp-Etchells Effect. The downward thrust from the blades kicks up a cloud of sand, and the blades smash into millions of these tiny particles. Every so often, the metal blasted from the blades produces a miniature meteor shower.