Since the 1980s, Gerta Keller, professor of paleontology and geology at Princeton, has been speaking out against an idea most of us take as scientific gospel: That a giant rock from space killed the dinosaurs. Nice story, she says—but it’s just not true. Gerta's been shouted down and ostracized at conferences, but in three decades, she hasn’t backed down. And now, things might finally be coming around for Gerta’s theory. But is she right? Did something else kill the dinosaurs? Or is she just too proud to admit she’s been wrong for 30 years?