Using some of the biggest telescopes ever built – marvels of engineering in their own right – he found that all the galaxies were racing apart from each other. Although born an American, Hubble had fallen for the charms of the English aristocracy and groomed himself into the quintessential English gentleman while studying in Oxford. With a cosmic yardstick for measuring the distance to the galaxies, Edwin Hubble made a remarkable discovery. Herman, Gamow and Alpher, who predicted an echo from the Big Bang.

When Cepheid variable stars were found in distant galaxies, it became possible to measure the distance to the galaxies. 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.

The code book by simon singh