The Fly in the Cathedral is a 2004 book by Brian Cathcart , telling the story of how physicists around the world, but particularly in the University of Cambridge's Cavendish Laboratory, split the atom in the 1930s.
The title refers to the size of the atomic nucleus in relation to the size of the whole atom. Although this analogy was made in the very early 20th century, many years before accurate figures were known, it turns out to be an appropriate illustration of the size difference, to within a couple of orders of magnitude.