At first, Hubble (1889–1953) is undecided whether to become a boxer or to study astronomy. Ultimately, he chooses the latter. At the Yerke Observatory he works on his dissertation on photographic studies of faint nebulae, which he completes in 1917. Afterwards, he is fortunate in being able to conduct research using the world’s largest telescopes - first at Mount Wilson, later at the Palomar Observatory. His work opens up an entirely new view of our universe. Using Cepheid stars, he calculates the distance to the Andromeda nebula. Hubble demonstrates that the Milky Way is merely one among many star systems, and that the galaxies are moving away from us, which leads to the conclusion that the universe is expanding. Hubble’s observations confirm the mathematician Friedmann’s cosmological interpretation of Einstein’s General Theory of Relativity.