- #1

*instantaneously*reversed direction, returning at the same speed, we can calculate that T1 aged only 4 years by using the standard Minkowski transformation for time.

If, on the other hand, observer O sees two travelers (T1 and T2) moving in opposite directions, then each should return to O having aged the same amount (symmetry principle). The problem I can't seem to figure out is how this is transferred to the points of view of T1 and T2. Since each is moving at 3c/5 relative to O, their speeds relative to each other should always be 15c/17 (relativistic velocity addition). Thus, it seems that each traveler sees the other traveler aging by 17*4/8=17*4/8=8.5 years, while they each measure their own time lapse to be 4 years.

Can anyone explain where I am not correctly translating the problem?

Thanks.