[ToC]

 

Jean-Pierre Luminet, Black Holes, Cambridge University Press, 1987

THE SPACE-TIME CONTINUUM OF SPECIAL RELATIVITY

At each event E in space-time light rays generate two cones. The light rays emitted by E span the future cone and those received by E span the past cone (shaded). Ordinary particles are unable to travel faster than the velocity of light, and their trajectories are confined to the interior of the cones. No light ray or particle which passes through E is able to penetrate the 'Elsewhere' (clear zone). The absolute invariance of the velocity of light in a vacuum is shown by the fact that all the cones have the same slope: the space-time continuum of Special Relativity, free from gravitating matter, is flat.