Father-son scientists Luis and Walter Alvarez piece together one of the greatest mysteries of all time: What really happened to the dinosaurs? Dive into this fun and informative middle grade nonfiction book, which outlines the many important scientific discoveries that aided the Alvarezes in their search for answers.Cretaceous earth was known as the age of dinosaurs. But really, it was the age of LIFE--scaled and feathered, furry and leathered, budding, blooming, roaring, zooming, buzzing, glorious LIFE--until... DOOMSDAY. For 66 million years, the mystery of what happened to the dinosaurs lay hidden under layers of sand and silt, until scientists began to piece together the puzzle of what happened on the last day of the ancient world. Follow the real-life adventures of father-son scientists Luis and Walter Alvarez--along with an army of science detectives--as they unlock the world's most intriguing mystery. Learn how the smallest particles in the universe helped explain what happened to the largest animals that ever walked the planet. Track the timelines of discoveries that had to happen in physics, paleontology, astronomy, and geology, before humans could understand how and why 75 percent of species suddenly went extinct. This is the story of how scientists add to the sum total of human knowledge, one question at a time, and help us understand our beautiful, tragic, and magnificent world.