Geometrie und Erfahrung

This concise volume contains two addresses by Dr. Einstein outlining aspects of the theories. "Ether and Relativity" (1920), delivered at the University of Leyden, discusses the properties demanded of the ether of space by the theory of relativity. "Geometry and Experience" (1921), given at the Prussian Academy of Sciences, describes the limits within which the Euclidean or any other practical geometric system can be held to be approximately true in connection with the concept of a finite universe.