The sad history of radioactive relationships must, by definition, begin with Marie Curie, the woman who coined the term “radioactivity.” In 1911 the widowed madame had an affair with the physicist Paul Langevin, a married former student of her late husband. The ensuing scandal, which was uncovered concurrently with the awarding of her second Nobel Prize, nearly cost her her reputation. And while this heated dalliance drives the story in Lauren Gunderson’s instructive new work, The Half-Life of Marie Curie, it is framed by another of Curie’s relationships, the platonic friendship she shared with the electrical engineer and suffragette Hertha Ayrton.