Looking back from the first decade of the 20th century, Herbert Hall Turner, Savilian Professor of Astronomy at Oxford, believed that ‘a revolution in almost all departments of Astronomy, theoretical and practical’ had recently taken place. He dated its beginning to about 1875, when the new techniques of photography and spectroscopy arrived at his then-workplace, the Royal Observatory, Greenwich. The revolution was in full swing by the 1880s, when Agnes Clerke hailed the ‘unexpected development of this new physical-celestial science’ and its ‘brilliant results’ in her A Popular History of Astronomy during the Nineteenth Century. The revolution shifted astronomy from an overriding focus on mapping the heavenly bodies and establishing the mechanics of their motions to exploring their chemistry and physics.

It is the arrival of this new astronomy that Dava Sobel describes in her latest book. Her ‘glass universe’ is that captured on photographic plates, which preserved the changing skies over years, showing even faint stars and spectra invisible to telescopic observers. They allowed painstaking measurement, computation and comparison, which, undertaken in offices during the day, was often carried out by women. The story Sobel tells is largely an institutional history of Harvard College Observatory, worth recounting because of the unusually large number of women involved and the influence of their findings (though the tale is not in any sense as hidden or as broad as the subtitle suggests). Williamina Fleming, Antonia Maury, Henrietta Swan Leavitt, Annie Jump Cannon and Cecilia Payne were among the most distinguished of those who, between 1877 and 1952, worked or volunteered under the observatory’s directors, Edward Pickering and Harlow Shapley. 

These directors are given credit for their positive attitude towards women in science, but Sobel skims over other reasons for the women’s presence. One was economic: Sobel insists that Pickering did not take advantage of his female workers, noting that he was ‘widely perceived as more than fair’, but she