We use the following formulas for the Lorentztransformation: x’ = [ x / sqrt(1-v**2/c**2)] - [vt / sqrt(1-v**2/c**2)] (1) and t’ = - [ (vx)/c**2 / sqrt(1-v**2/c**2)] + [ t / sqrt(1-v**2/c**2)] (2) The twin paradox reads as follows. Gea and Stella are identical twins. Stella leaves from earth for an interstallar journey with a constant velocity v, where 0 < v. According to the Lorentztransformation Stella's clock will be slower then Gea's clock. Therefore Stella will be younger then Gea when returning back to earth. However, due to the symmetry of the situation Gea's clock will also be slower then Stella's clock, which leads to a paradox. We choose the following situation for Stella's yourney. In the beginning of the story Stella travels from the earth a distance of three light years with a constant velocity 0.6*c. Then she returns back instantneously and travels the same distance back with the same constant veocity. If we take c = 1, then the time she travels untill the point of returning is equal to 3 / 0.6 = 5. Shortly, x = 3, v = 0.6 en t = 5. The time she will need to travel back is equal to the time she needed to travel to the returning point. Therefore the total total time of her yourney, calculated from the viewpoint of Gea (x,t), is equal to 5 + 5 = 10. However, according to formula (2), the time Stella travels untill the point of returning, calculated from the viewpoint of Stella (x',t'), is equal to 4. Therefore the total total time of her yourney, calculated from the viewpoint of Stella, is equal to 4 + 4 = 8. So we have t / t' = 10 / 8 = 1.25. If we take as our steady reference system (x,t) Stella, then taken from her viewpoint, Gea would travel towards her returning point, with a velocity -v with 0 < v, and according to formula (2) the time untill the point of returning, calculated from the viewpoint of Gea (x',t'), is equal to 6.25. The total time for Stella, calculated from the viewpoint of Stella, would be 5 + 5 = 10 and total time for Gea, calculated from the viewpoint of Gea, would be 6.25 + 6.25 = 12.5 and again the ratio t / t' = 1.25. Therefore, actuall there is no paradox. It seems however, that, in this way of reasoning, v should represent a number wich is larger then zero: 0 < v. Is this correct?