The Heroic Discovery of Other Galaxies

S1, E4: How did Henrietta Swan Leavitt, the prolific discoverer of variable stars, make sense of “Cepheid variables”? How did she calculate the relationship between their periods and their true luminosities? How did Edwin Hubble use Leavitt’s work (known as the Leavitt law) to measure the distance to the Great Andromeda Nebula in the 1920s?