31: Purely Geometric Part of Dark Matter

Plots of orbital velocities of stars of galaxies as a function of their distance from the center show a great surprise: They do not decrease with distance in a way that would be expected from an ordinary gravitational field created by the visible masses. This lead F. Zwicky [1] in 1933 to postulate the existence of dark matter. In fact, the observed velocity curves ask for large amounts of invisible matter in each galaxy. The presently best theoretical fit to the data is shown in Fig. 31.1, and the reader is referred to the original publication dealing with this issue [2]…