Relativity, Twin Paradox, Time Dilation, Lenghts Contraction, Lorentz Transformation.
the spaceship S_1 is empty with only the spaceship in the origin. We get then t > t_1. The astronaut twin is mistaken in thinking that he is his own alter ego and, even if he sees the Earth in motion, it’s t > t_1. (he is always younger than the stationary observers of the frame of the Earth S) If