At the beginning of the twentieth century, scientists argued over the size of the universe: was it, as the astronomer Harlow Shapley argued, the size of the Milky Way, or was there more truth to Edwin Hubble�s claim that our own galaxy is just one among billions?

The answer to the controversy�a �yardstick� suitable for measuring the cosmos�was discovered by Henrietta Swan Leavitt, who was employed by the Harvard Observatory as a number cruncher, at a wage not dissimilar from that of workers in the nearby textile mills. Miss Leavitt�s Stars uncovers her neglected history, and brings a fascinating and turbulent period of astronomical history to life.