This English translation of the paper by F. Zwicky, “Die Rotverschiebung von extragalaktischen
Nebeln”, Helv. Phys. Acta 6, 110–127 (1933), in which he concluded
from the results of observations that the amount of non-luminous matter in the Universe must be greater
than that of luminous matter—thus becoming an early precursor of the dark matter idea, has been
selected for publication in the Golden Oldies series of General Relativity and Gravitation. The paper is accompanied by an editorial
note written by Jürgen Ehlers and by Zwicky’s brief biography compiled by Andrzej Krasiński.