Stony evidence of the hellfire that drove dinosaurs to extinction

WHEN, IN 1980, Luis Alvarez, a physicist, and his son Walter, a geologist, made public their theory that the dinosaurs were killed by a massive asteroid strike, it came as a curveball to palaeontologists, who believed dinosaurs had gradually died out through other means. The father-and-son team from the University of California, Berkeley, argued that evidence of the catastrophe was hiding in plain sight, the world over, as a thin layer of sediment enriched in iridium, a metal commonly found in a...