Why there are no non-avian dinosaurs on Earth today?
Luis Alvarez, nuclear physicist and his son Walter Alvarez, geologist near the geological section of the K-T boundary near the town of Gubbio in Italy. The examination of the iridium content of the sample taken from the thin reddish clay between the two ancient limestone layers led to the hypothesis named after them. That is the extinction at the end of the Cretacous was induced by a meteorite impact.