Nalaka Gunawardene, a friend and colleague, has provided an overview of the hazards posed by near-earth objects. Thousands of pieces of cosmic debris enter our atmosphere every day — most are burned up before hitting the ground (producing harmless ‘shooting stars’). Larger pieces that crash-land are called meteorites. Even then, average ones are too small to cause much damage. Once in a while, a large enough piece comes along — as did on February 15 – which can be an asteroid or part of a comet.