Anisotropic Cosmologies: From a Slow Start in the 1920s to an Explosion of Interest in the 1950s and Beyond

In 1921, Edward Kasner published the first anisotropic exact solution to Einstein's field equations of general relativity. As a vacuum solution, Kasner did not imply it was physically realistic. Three decades passed before Abraham Taub published a richer picture of exact solutions, aimed at investigating Mach's Principle. That work, and the goal of resolving the horizon problem helped inspire Charles Misner to propose the Mixmaster Universe, around the same time as the Belinski–Khalatnikov–Lifshitz singularity research, each focused on the Bianchi type IX anisotropic cosmology. We will examine the factors that led to the 30 year gap between Kasner and Taub's work, and the subsequent explosion of interest in such models with the aim of investigating the nature of the initial cosmological singularity.