OK, so I'm pretty familliar with the regular twin paradox and the explinations of how you decide which twin is younger by noticing which one accelerated, and the geometrical view of this using k-calculus and minkowsky diagrams, etc. I just thought of something though, and I guess my relativity isn't strong enough to think of a solution, at least not in the period of time it took me to go make some tea Suppose that we live in a closed universe, for simplicity's sake let's also assume that universe is balanced with a cosmological constant so that it is neither expanding nor contracting (ala Einstein's static universe model). If I'm in a spaceship and I go flying by my friend at a very high velocity, and then wait for some time, I should wrap around and go flying past him a second time. If we set both our clocks to zero at the first flyby, what will our clocks read when we pass eachother the second time? I'm at a loss to try and explain any differences in the clocks without attaching a prefered reference frame to "the surface of the universe" which my friend is allegedly still with respect to, which of course sets off all of my in-built relativity alarms. I'm tempted to say that we'll both have the same number on our watches when we pass the second time and ascribe it to a general relatavistic "you can't compare time or space intervals at a distance" effect.