Hi all, apologies if this has been posted a million times before.... I'm trying to explain the twin paradox without getting involved with length contraction. One way to think of it is Twin A remains at rest on Earth then twin B goes off at 4c/5 to Alpha centauri 4 light years away, then comes back again having aged 6 years, 3/5 as much as twin A. Alternatively, can I think about it this way? Twin B remains at rest, while twin A and Alpha centauri speed off at 4c/5 for 5 years in the rest frame of B. When Alpha centauri reaches twin B, he suddenly accelerates to 40c/41 (relativistically added 4c/5 and 4c/5) and catches Twin A up. The lorentz factor of twin B becomes 41/9...and from here I struggle to get the nice and simple Twin A = 10 years, Twin B = 6 years like I did before. Any advice?