These women toiled tirelessly, marking times, coordinates and other notations for photographic images of the sky taken nightly and preserved on glass plates — the glass universe. Using diaries, letters, memoirs and scientific papers, Sobel recounts the accomplishments of these extraordinary women, going into enough scientific detail (glossary included) to satisfy curious readers and enough personal detail to bring these women’s stories to life. Sobel takes readers through World War II and a myriad of other moments starring women: first woman observatory head; first woman professor at Harvard (of astronomy, of course); discoveries of binary stars, the prevalence of hydrogen and helium in stars, and the existence of interstellar dust.