Carl Wilhelm Wirtz (24 August 1876 in Krefeld – 18 February 1939 in Hamburg) was an astronomer who studied astronomy at Bonn University (1895-1898) obtaining his doctorate there [1] after which he spent his time between the Kiel Observatory (526) in Germany and the Observatory of Strasbourg, France.

[2] As already Vesto Slipher in 1912,[3] Wirtz in 1918 observed a systematic redshift of spiral nebulae, which was difficult to interpret in terms of a cosmological model in which the Universe is filled more or less uniformly with stars and nebulae.

[4] He wrote:[5] It is remarkable, that our system of fixed stars shall have such a very strong displacement of 820 km/s, and equally strange is the interpretation of the systematic constant k = + 656 km.

If we ascribe a verbatim interpretation to this value, then this means that the system of spiral nebulae is drifting apart by a velocity of 656 km with respect to the momentary location of the solar system as the center.In 1922,[6] he wrote a paper where he argued that the observational results suggest, that the redshifts of distant galaxies are becoming higher than more closer ones, which he interpreted as an increase of their radial velocities with distance, and that larger masses have smaller redshifts than smaller ones.

[9] In 1936, Wirtz wrote a short paper alluding to the priority for his 1922-conclusion that the radial velocities of galaxies are increasing with their distance.