" The Perseids are caused by the debris left behind by comet Swift-Tuttle, which is one of the bigger comets in the solar system. And every year in middle of August we run into the debris trail. And when that debris hits our atmosphere at 132,000 miles per hour, it burns up and leaves these brilliant streaks of light we call Perseid meteors." - Bill Cooke This week on Living Lab Radio: Suzanne Schindler of Washington University in St. Louis says a new blood test for Alzheimer's disease could be