![]() She realised that the rate of variation of a Cepheid star gave a strong indication of its actual brightness, which could then be compared with its apparent brightness as seen from Earth, which then indicated the distance to the star. With a great leap of intuition, she showed that Cepheid variable stars, which vary periodically in brightness, could be used to measure distances across the universe. ![]() Working as a ‘computer’ in the days when few women could pursue a career in science, she was employed to measure and analyse photographs of the stars in painstaking detail. Henrietta Leavitt was the woman who rescued the situation. In particular, nobody could measure the distances to the galaxies. Even measuring distances across the universe had proved problematic. Unfortunately, they were having serious problems with measuring reality. ![]() While theorists developed this hypothesis, it was up to the observational astronomers to test the theory against reality. (Courtesy of Harvard College Observatory) Henrietta Leavitt Inventor of the cosmic yardstick. ![]()
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