TY - JOUR T1 - O paradoxu dvojčat A1 - Křížek, Michal JA - Obzory matematiky, fyziky a informatiky Y1 - 2021 VL - 50 IS - 2 SP - 1 EP - 10 SN - 1335-4981 N2 - First we present several illustrative examples of the classical twin paradox, since there are still many doubts and conjectures about it. Further, we show that time in a gravitational field on the surface of a spherically symmetric mass body flows as quickly as the proper time of a clock moving by the corresponding second cosmic speed. ER -