Helge Kragh is a historian of science, presently working as an emeritus professor at the Niels Bohr Institute, Copenhagen. His previous publications, both articles and books, have dealt with Niels Bohr and his atomic theory, most comprehensively in Niels Bohr and the Quantum Atom published by Oxford University Press in 2012. Altogether he has published more than 30 books, about 20 of them in English.