"Shortly after Einstein published his original memoir... de Sitter constructed an alternative static world-model... unlike Einstein's, space-time has an intrinsic structure of its own, independent of the presence of matter. ...there is, strictly speaking, no matter or radiation. ...whereas a test particle in Einstein's universe will remain at rest if it has no initial motion, a similar particle introduced in de Sitter's world will immediately acquire an ever-increasing velocity of recession from the observer. Moreover, in de Sitter's model, space-time is 'hyperbolic'. There is no absolute time, and each observer will perceive a horizon at which time will appear to him to stand still. ...This phenomenon. of course, is only apparent, like a rainbow. At any point on the (relative) horizon the time-flux experienced by an observer there will be the same as the original observer. Thus in de Sitter's world there will be an apparent slowing-down of distant atomic vibrations, if these keep standard time. Consequently the radiation from a distant nebula will appear to be shifted toward the red... This effect, of course, will be supplemented by the Doppler effect, due to the relative recession of the nebula regarded as a test particle."