Relativity: 300 years from a principle to reality

This technical note provides a brief background to the historical developments that led to the generalization of Galileo's principle of relativity, leading to Einstein's general theory of relativity. Therefore, its primary purpose is to mark the contributions made in physics of motion on this occasion—the marking of the new Millennium. To keep with the tradition set in this journal, this note contains a new analysis in respect of reported super-luminal observations in gain-assisted light propagation, in particular vis-à-vis their concordance with the general theory of relativity. The incompleteness principle, as an axiom of observation, is introduced here to resolve this issue.