Theoretically predicted adatom diffusion mechanism on the fcc surface of some common metals, including Copper, Aluminum, Silver, Gold, Paladium, Platinum, and Nickel. A single atom makes a knight's move across the surface via the illustrated exchange. The primary atoms are colorized for demonstration purposes. All atoms are of the same element. Credit: J.M. Cohen, Los Alamos Nat. Lab, New Mexico Tech, 4Physics.
Why does a returning boomerang come back?
When most of us think of boomerangs, we imagine somebody throwing a curved stick that eventually turns around and comes right back to the thrower's hand. This device is simply amazing, and a wonderful application of some laws of physics relating to aerodynamic lift and angular momentum.