Number one New York Times best-selling author Dava Sobel returns with a captivating, little-known true story of women in science. In the mid-19th century, the Harvard College Observatory began employing women as calculators, or 'human computers', to interpret the observations their male counterparts made via telescope each night. As photography transformed the practice of astronomy, the women turned to studying images of the stars captured on glass photographic plates, making extraordinary discoveries that attracted worldwide acclaim. They helped discern what the stars were made of, divided them into meaningful categories for further research, and even found a way to measure distances across space by starlight. Elegantly written and enriched by excerpts from letters, diaries, and memoirs, The Glass Universe is the hidden history of a group of remarkable women whose vital contributions to the burgeoning field of astronomy forever changed our understanding of the stars and our place in the universe.