The Norwegian and the Englishman

I sketch the lives and work of the Norwegian physicist Kristian Birkeland (1867–1917) and the English mathematician Sydney Chapman (1888–1970), focusing particularly on Chapman’s controversy with Birkeland over the origin and development of auroras, a controversy that Chapman conducted with Birkeland for more than fifty years after Birkeland’s death. Sidney Borowitz is Professor Emeritus of Physics at New York University.