Guardian: Say I were to ask you to prove that the dinosaurs were wiped out when an asteroid collided with the Earth 66m years ago, in what is now snappily called the Cretaceous-Paleogene extinction event.
If you were as weirdly obsessed by these catastrophes as I am, you would maybe start by citing the worldwide layer of sediment known as K-Pg boundary, which was first discovered near Gubbio, in Italy, and is thought to be the fallout from a massive explosion. You would mention the soot that is associated...