I`ve thought about a special sort of twin paradox. I know the usual explanation of the twin paradox but give me please the answer to this special case: Imagine: A static universe (non-expanding) with a closed geometry and a circumference of one lightyear. The twins start their journey in different direction from their planet (EARTH2) with nearly light speed. <-------- [TWIN1] [EARTH2] [TWIN2] --------> Here is my question: When they will met again after one year on EARTH2 -- which twin is the younger one? The answer to my question isn`t so easy to give as it seems. Please think correctly. You may try this answer: Twin 1 travels in the system of twin 2 and therefore he ages less because of the time-slowing, conclusion: he has a different age! This answer is in contradiction with the principle of relativity! You may try perhaps this answer: They both travel the same journey, the conclusion is: - they both have the same age. Now you have a serious problem. Twin 1 had placed 1000 clocks along the circumference of the universe. The clocks have all the same distance between them - and they also move exactly in the same direction and with the same velocity like twin 1 does. Imagine now twin 1 synchronises all these moving clocks with his own clock. They all show the same time in the system of twin 1. Twin 1 says: I see my twin moves forward from clock1 to clock2 and so on and so I can see that his own slow-down-time conforms to Einsteins theory of relativity. When my twin finally reaches clock999 to clock1000 and EARTH2 he is finally jounger than me. Twin 2 makes the same experiment with another set of 1000 clocks. Twin 2 says: I see my twin moves forward from clock1 to clock2 and so on and so I can see that his own slow-down-time conforms to Einsteins theory of relativity. When my twin finally reaches clock999 to clock1000 and EARTH2 he is finally younger than me too! What are you thinking now? Who`s one is right? Please don`t give the usual answer to me I have to search the solution in the general theory of relativity. That`s no answer at all. My question is: Which twin is actually the younger one? - or have both the same age? What answer gives us the general theory to this question? Is there no time-slowing at all?! Please answer the question. In my opinion there is no solution to this question. This paradox shows: In our universe the special theory of relativity is right. I agree. But in a closed universe it can`t be right, conclusion: we don`t live in a closed universe. Think you got to know this. That`s all!