Writing in 2008, American scientist and author Carl Zimmer introduces the third edition of T. Rex and the Crater of Doom. He recalls how he first heard about Alvarez’s impact hypothesis as a teen and was fascinated by its possibilities. As Zimmer began his career as a science writer, he continued to follow the development of Alvarez’s theory that a massive asteroid collision in the late Cretaceous period triggered the mass extinction of the dinosaurs. Zimmer observes that this theory “continued to mature” (ix) as it was tested and refined with new discoveries over the years (ix).

Supported by geological and paleontological evidence, Alvarez’s impact theory marked a shift away from uniformitarianism, a school of thought dictating that Earth evolved through gradual, tiny changes. Impact theory showed that while Earth has experienced cumulative change over long periods, it has also been profoundly shaped by singular, catastrophic events, such as asteroid impacts.

Alvarez’s work raised new questions for geologists and space researchers about Earth’s “geological trauma,” such as the effects of other collisions, or the possibility that other asteroids planted the seeds of life on Earth in a process called “panspermia.