famous paradox, everyone should knows it. Whenever Ive heard it though its been dismissed as not really being a paradox since the two twins paths arent identical. The twin in the rocket accelerates off earth and then accelerates back. With a hyper-spherical universe however you could have this done without any acceleration (to make it perfect you can replace the twins with clocks calibrated as the rocket passes earth at some high velocity) since anything going away from earth in a straight line will eventually arrive back at earth. I did some quick calculations earlier with a 10^10 m circumference of the universe and a rocket going at .8c. I got that the rocket twin arrives back at earth in 25 seconds (distance is shortened to 6x10^9 which divided by .8c is 25) while the twin on earth ages 70 seconds (time goes faster for him as earth moves away and dt = 5/3). I may of gotten the second part wrong because if you think about it from the earth twins frame he just watches the other twin travel 10^10m at .8c which is about 40 seconds. Can someone do the math right for me before I comment on the paradox? (if there is one).