As Earth orbits the sun, it continually ploughs through dust and debris left behind by passing comets and asteroids. On any night of the year, a keen-eyed observer might see five, or even ten, meteors (shooting stars) per hour. But over the next week, that number will rise markedly, as Earth moves through the centre of a stream of debris left behind by the most famous of all comets, comet 1P/Halley.