The twin thing has been beat to a pulp on these forums - so maybe this got resolved somewhere along the way - if so - someone can point me to the solution. Otherwise here is the set-up. Assume two satellites are placed in orbit around a black hole, one is in circular orbit, the other highly elliptical - we specify observers A and B with clocks in each saterllite in gimbled suspension structures to eliminate any awareness that the satellite is in motion - so since the observers can't see the black hole G source and they do not turn or rotate or tilt during their orbit, they think they are at rest. To complete the illusion, we can blank our the light from the universe so illusion is complete: each observer is firmly convinced he is not moving. The two satellite orbits are adjusted so their paths cross every 100 years as seen from earth - on the first crossing, each sets his clock to zero, when they pass nearby after a 100 years each checks the others time - which clock has logged the larger amount of time and why? Since each observer believes he is in an inertial frame and can observe the other satellite going off doing wild girations including accelerations and decelerations and returning, he would tend to conclude the other dude is younger. From observer A's perspective B has taken a long trip and returned - But B see's A flashing past and watches him return - so B should be able to claim A is the round trip traveler and is younger This presupposes no other visual reference frames to give away the motion and also that any orbit (whether circular or ellipitical) is a good inertial frame.