The Motion of Galaxies in Galaxy Clusters
Zwicky’s observation of the unexpectedly high velocities of the individual galaxies in the cluster of galaxies known as the ComaCluster led to the first appearance of the dark matter hypothesis. Unlike the organized motions in a nearly steady-state of the individual stars in a single spiral galaxy, the galaxies within a cluster are generally observed to move chaotically. Since we are not yet in a position to model such intrinsically time-dependent chaotic systems in General Relativity, we took the first step in the direction of dealing with time-dependence, again with an idealization. In what follows, we will describe our idealized model that brings into play intrinsic time-dependence. As a bonus, we are able to counter some of the criticism that had been levied against our earlier work.