Abstract: The asymmetry between the roads "going" and "return" of light signal in a moving system K' (regarding system Ko of light) can be caught only with unidirectional signals. Such case constitutes the observation of Roemer (1676). Roemer measures the period T of rotation of the satellite Yo around Jupiter (stationary system K), using the unidirectional rays of Yo to the Earth (moving system K') in staging closed by Earth's orbit. Thus detects unclarified in depth timing differences between the zones of moving away and approach of the Earth to Yo, carelessly neglected by the relativism.
