The Redshift of Extragalactic Nebulae

This gives a description of the most essential characteristics of extragalactic nebulae, as well as of the methods used to investigate these. In particular, the so-called redshift of extragalactic nebulae is discussed in detail. Various theories which have been proposed to explain this important phenomenon, are briefly discussed. Finally, it will be indicated to what extent the redshift promises to become of importance for the study of cosmic rays.