Inside Harvard College Observatory in 1904, a young woman named Henrietta Swan Leavitt sat hunched over a stack of glass photographic plates, patiently counting stars. The images had been taken by a telescope high in the Peruvian Andes, and Miss Leavitt was given the tedious chore of measuring the brightness of thousands of tiny lights, something that would now be done by machine. Her job title was \'computer,\' but during the next few years she rose above her station as a tabulator of data and discovered a new law, one that would change forever our view of the universe. George Johnson, the author of Miss Leavitt\'s Stars: The Untold Story of the Woman Who Discovered How to Measure the Universe, writes about science for The New York Times from Santa Fe, New Mexico and is winner of the AAAS Science Journalism Award. His other books include A Shortcut Through Time: The Path to the Quantum Computer, Fire in the Mind: Science, Faith, and the Search for Order and Strange Beauty: Murray Gell-Mann and the Revolution in 20th-Century Physics. He is co-director of the Santa Fe Science-Writing Workshop and can be reached on the Web at talaya.net. A graduate of the University of New Mexico and American University, his first reporting job was covering the police beat for the Albuquerque Journal.