Emeritus Professor at the Niels Bohr Institute in Copenhagen, Helge Kragh is the author of numerous books on physics and cosmology, including the first full-length biography of Paul Dirac, Dirac: A Scientific Biography. Among his other books are Cosmology and Controversy (1999), Quantum Generations: A History of Physics in the Twentieth Century (2002), and Conceptions of Cosmos (2013).