Spatial Directions, Anisotropy and Special Relativity

Abstract

The concept of an objective spatial direction in special relativity is investigated and theories assuming light-speed isotropy while accepting the existence of a privileged spatial direction are classified. A natural generalization of the proper time principle is introduced which makes it possible to devise experimental tests of spatial isotropy. Several common misunderstandings in the relativistic literature concerning the role of spatial isotropy are clarified.Comment: 24 pages, 2 figures. Final enlarged and slightly corrected version. Keywords: relativity, very special relativity, spatial isotropy, reciprocity, differential aging; Foundations of Physics, 201