The Perseid meteors are bits of 2,000-year-old debris left behind by the periodic comet Swift-Tuttle. Earth’s atmosphere collides with the debris at more than 38 kilometers (23 miles) a second. Meteors generally get incinerated before they can strike the ground, creating the streaks of superheated, glowing air we call shooting stars. A “shooting star” streaks over Canada’s Quebec Province during the Perseid meteor shower on August 12, 2008. Photograph by Michael Tournay, My Shot

Tonight (Tuesday 8/11/2009), from any vantage point in the world, you might see more than 80 meteors an hour streak across the sky during the best viewing time, when the moon’s glare will be weakest—late night and into the wee hours of Wednesday, local cloud and lighting conditions permitting.